diff --git a/modules/aws/alternate-contacts/backplane/README.md b/modules/aws/alternate-contacts/backplane/README.md
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+---
+name: AWS Alternate Contacts Backplane
+supportedPlatforms:
+- aws
+description: |
+  Backplane infrastructure for the AWS Alternate Contacts building block.
+---
+
+This module sets up the IAM user and StackSet-based role deployment needed to manage alternate contacts on AWS accounts in your organization.
+
+It creates:
+
+1. An **IAM User** in your backplane account with permission to assume a service role in target accounts.
+2. A **CloudFormation StackSet** deployed to the specified OUs that creates a service role in each target account with the necessary `account:*AlternateContact` permissions.
+
+## Usage
+
+```hcl
+module "alternate_contacts_backplane" {
+  source = "./modules/aws/alternate-contacts/backplane"
+
+  building_block_target_ou_ids = ["ou-xxxx-xxxxxxxx"]
+
+  providers = {
+    aws.management = aws.management
+    aws.backplane  = aws.backplane
+  }
+}
+```
+
+<!-- BEGIN_TF_DOCS -->
+## Requirements
+
+| Name | Version |
+|------|---------|
+| <a name="requirement_terraform"></a> [terraform](#requirement\_terraform) | >= 1.3.0 |
+| <a name="requirement_aws"></a> [aws](#requirement\_aws) | ~> 5.0 |
+
+## Modules
+
+No modules.
+
+## Resources
+
+| Name | Type |
+|------|------|
+| [aws_cloudformation_stack_set.permissions_in_target_accounts](https://registry.terraform.io/providers/hashicorp/aws/latest/docs/resources/cloudformation_stack_set) | resource |
+| [aws_cloudformation_stack_set_instance.permissions_in_target_accounts](https://registry.terraform.io/providers/hashicorp/aws/latest/docs/resources/cloudformation_stack_set_instance) | resource |
+| [aws_iam_access_key.backplane](https://registry.terraform.io/providers/hashicorp/aws/latest/docs/resources/iam_access_key) | resource |
+| [aws_iam_user.backplane](https://registry.terraform.io/providers/hashicorp/aws/latest/docs/resources/iam_user) | resource |
+| [aws_iam_user_policy.assume_roles](https://registry.terraform.io/providers/hashicorp/aws/latest/docs/resources/iam_user_policy) | resource |
+| [aws_iam_policy_document.building_block_service](https://registry.terraform.io/providers/hashicorp/aws/latest/docs/data-sources/iam_policy_document) | data source |
+| [aws_partition.current](https://registry.terraform.io/providers/hashicorp/aws/latest/docs/data-sources/partition) | data source |
+
+## Inputs
+
+| Name | Description | Type | Default | Required |
+|------|-------------|------|---------|:--------:|
+| <a name="input_backplane_user_name"></a> [backplane\_user\_name](#input\_backplane\_user\_name) | n/a | `string` | `"building-block-alternate-contacts"` | no |
+| <a name="input_building_block_target_account_access_role_name"></a> [building\_block\_target\_account\_access\_role\_name](#input\_building\_block\_target\_account\_access\_role\_name) | Name of the role that the backplane user will assume in the target account | `string` | `"building-block-alternate-contacts"` | no |
+| <a name="input_building_block_target_ou_ids"></a> [building\_block\_target\_ou\_ids](#input\_building\_block\_target\_ou\_ids) | List of OUs that the building block can be deployed to. Accounts in these OUs will receive the building\_block\_backplane\_account\_access\_role | `set(string)` | n/a | yes |
+| <a name="input_stackset_region"></a> [stackset\_region](#input\_stackset\_region) | AWS region to deploy the StackSet instances in | `string` | `"eu-central-1"` | no |
+
+## Outputs
+
+| Name | Description |
+|------|-------------|
+| <a name="output_aws_access_key_id"></a> [aws\_access\_key\_id](#output\_aws\_access\_key\_id) | Access key for the IAM user that can set alternate contacts |
+| <a name="output_aws_secret_access_key"></a> [aws\_secret\_access\_key](#output\_aws\_secret\_access\_key) | Secret key for the IAM user that can set alternate contacts |
+| <a name="output_role_name"></a> [role\_name](#output\_role\_name) | Name of the IAM role assumed in target accounts to set alternate contacts |
+<!-- END_TF_DOCS -->
diff --git a/modules/aws/alternate-contacts/backplane/main.tf b/modules/aws/alternate-contacts/backplane/main.tf
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+++ b/modules/aws/alternate-contacts/backplane/main.tf
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+# AWS Alternate Contacts Backplane
+# This module creates necessary IAM Users and role setup so that we have an IAM user that can set alternate contacts
+# on any account in the target OU.
+
+# user referenced in building block definition
+resource "aws_iam_user" "backplane" {
+  provider = aws.backplane
+  name     = var.backplane_user_name
+}
+
+resource "aws_iam_access_key" "backplane" {
+  provider = aws.backplane
+  user     = aws_iam_user.backplane.name
+}
+
+data "aws_partition" "current" {
+  provider = aws.backplane
+}
+
+# access building block service role in target accounts
+data "aws_iam_policy_document" "building_block_service" {
+  provider = aws.backplane
+  version  = "2012-10-17"
+  statement {
+    effect    = "Allow"
+    actions   = ["sts:AssumeRole"]
+    resources = ["arn:${data.aws_partition.current.partition}:iam::*:role/${var.building_block_target_account_access_role_name}"]
+  }
+}
+
+resource "aws_iam_user_policy" "assume_roles" {
+  provider = aws.backplane
+  name     = "assume-roles"
+  user     = aws_iam_user.backplane.name
+  policy   = data.aws_iam_policy_document.building_block_service.json
+}
+
+
+# this stackset automatically deploys the building block backplane role to target accounts
+resource "aws_cloudformation_stack_set" "permissions_in_target_accounts" {
+  provider         = aws.management
+  name             = var.building_block_target_account_access_role_name
+  permission_model = "SERVICE_MANAGED"
+  auto_deployment {
+    enabled                          = true
+    retain_stacks_on_account_removal = false
+  }
+  operation_preferences {
+    failure_tolerance_count = 50
+    max_concurrent_count    = 50
+  }
+
+  template_body = jsonencode({
+    AWSTemplateFormatVersion = "2010-09-09",
+    Description              = "Grants the building block backplane ${aws_iam_user.backplane.name} access to manage alternate contacts on a managed account.",
+    Resources = {
+      BuildingBlockServiceRolePermissions = {
+        Type = "AWS::IAM::Role",
+        Properties = {
+          RoleName = var.building_block_target_account_access_role_name,
+          AssumeRolePolicyDocument = {
+            Version = "2012-10-17",
+            Statement = [
+              {
+                Effect = "Allow",
+                Principal = {
+                  AWS = aws_iam_user.backplane.arn
+                },
+                Action = "sts:AssumeRole"
+              }
+            ]
+          },
+          Policies = [
+            {
+              PolicyName = var.building_block_target_account_access_role_name
+              PolicyDocument = {
+                Version = "2012-10-17",
+                Statement = [
+                  {
+                    Effect = "Allow",
+                    Action = [
+                      "account:PutAlternateContact",
+                      "account:GetAlternateContact",
+                      "account:DeleteAlternateContact",
+                    ],
+                    Resource = "*"
+                  }
+                ]
+              }
+            }
+          ]
+        }
+      }
+    }
+  })
+
+  capabilities = ["CAPABILITY_IAM", "CAPABILITY_NAMED_IAM"]
+
+  lifecycle {
+    ignore_changes = [administration_role_arn]
+  }
+}
+
+resource "aws_cloudformation_stack_set_instance" "permissions_in_target_accounts" {
+  provider = aws.management
+  deployment_targets {
+    organizational_unit_ids = var.building_block_target_ou_ids
+  }
+
+  region         = var.stackset_region
+  stack_set_name = aws_cloudformation_stack_set.permissions_in_target_accounts.name
+}
diff --git a/modules/aws/alternate-contacts/backplane/outputs.tf b/modules/aws/alternate-contacts/backplane/outputs.tf
new file mode 100644
index 00000000..daeff043
--- /dev/null
+++ b/modules/aws/alternate-contacts/backplane/outputs.tf
@@ -0,0 +1,15 @@
+output "aws_access_key_id" {
+  description = "Access key for the IAM user that can set alternate contacts"
+  value       = aws_iam_access_key.backplane.id
+}
+
+output "aws_secret_access_key" {
+  description = "Secret key for the IAM user that can set alternate contacts"
+  sensitive   = true
+  value       = aws_iam_access_key.backplane.secret
+}
+
+output "role_name" {
+  description = "Name of the IAM role assumed in target accounts to set alternate contacts"
+  value       = var.building_block_target_account_access_role_name
+}
diff --git a/modules/aws/alternate-contacts/backplane/variables.tf b/modules/aws/alternate-contacts/backplane/variables.tf
new file mode 100644
index 00000000..34b43f0a
--- /dev/null
+++ b/modules/aws/alternate-contacts/backplane/variables.tf
@@ -0,0 +1,22 @@
+variable "backplane_user_name" {
+  type     = string
+  nullable = false
+  default  = "building-block-alternate-contacts"
+}
+
+variable "building_block_target_account_access_role_name" {
+  type        = string
+  description = "Name of the role that the backplane user will assume in the target account"
+  default     = "building-block-alternate-contacts"
+}
+
+variable "stackset_region" {
+  type        = string
+  description = "AWS region to deploy the StackSet instances in"
+  default     = "eu-central-1"
+}
+
+variable "building_block_target_ou_ids" {
+  type        = set(string)
+  description = "List of OUs that the building block can be deployed to. Accounts in these OUs will receive the building_block_backplane_account_access_role"
+}
diff --git a/modules/aws/alternate-contacts/backplane/versions.tf b/modules/aws/alternate-contacts/backplane/versions.tf
new file mode 100644
index 00000000..1b1be9e1
--- /dev/null
+++ b/modules/aws/alternate-contacts/backplane/versions.tf
@@ -0,0 +1,20 @@
+terraform {
+  required_version = ">= 1.3.0"
+  required_providers {
+    aws = {
+      source  = "hashicorp/aws"
+      version = "~> 5.0"
+
+      configuration_aliases = [
+        # This provider needs to point at the account owning your AWS Organization
+        # or the delegated admin account that can deploy StackSets over your AWS Organization.
+        aws.management,
+
+        # This provider needs to point at the account that will host the IAM User for the building block backplane.
+        # Typically this is a dedicated account only used for building block automation.
+        aws.backplane
+      ]
+    }
+  }
+}
+
diff --git a/modules/aws/alternate-contacts/buildingblock/README.md b/modules/aws/alternate-contacts/buildingblock/README.md
new file mode 100644
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+++ b/modules/aws/alternate-contacts/buildingblock/README.md
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+---
+name: AWS Alternate Contacts
+supportedPlatforms:
+- aws
+description: |
+  Sets the alternate contact information (billing, operations, security) for an AWS account.
+---
+
+This Terraform module configures the alternate contacts for an AWS account. AWS alternate contacts are used to receive notifications for billing, operations, and security-related communications, ensuring the right people are contacted for each concern.
+
+Each contact type is optional -- set only the ones you need. AWS allows exactly one contact per type (billing, operations, security). Each contact requires a name, title, email, and phone number.
+
+## Usage Examples
+
+Set only a security contact:
+
+```hcl
+security_contact = {
+  name  = "Jane Doe"
+  title = "Security Officer"
+  email = "security@example.com"
+  phone = "+1-555-555-0100"
+}
+```
+
+Set billing and security contacts, skip operations:
+
+```hcl
+billing_contact = {
+  name  = "Carlos Salazar"
+  title = "CFO"
+  email = "billing@example.com"
+  phone = "+1-555-555-0199"
+}
+
+security_contact = {
+  name  = "Jane Doe"
+  title = "Security Officer"
+  email = "security@example.com"
+  phone = "+1-555-555-0100"
+}
+```
+
+## Permissions
+
+Please reference the [backplane implementation](../backplane/) for the required permissions to deploy this building block.
+
+<!-- BEGIN_TF_DOCS -->
+## Requirements
+
+| Name | Version |
+|------|---------|
+| <a name="requirement_terraform"></a> [terraform](#requirement\_terraform) | >= 1.3.0 |
+| <a name="requirement_aws"></a> [aws](#requirement\_aws) | ~> 5.0 |
+
+## Modules
+
+No modules.
+
+## Resources
+
+| Name | Type |
+|------|------|
+| [aws_account_alternate_contact.billing](https://registry.terraform.io/providers/hashicorp/aws/latest/docs/resources/account_alternate_contact) | resource |
+| [aws_account_alternate_contact.operations](https://registry.terraform.io/providers/hashicorp/aws/latest/docs/resources/account_alternate_contact) | resource |
+| [aws_account_alternate_contact.security](https://registry.terraform.io/providers/hashicorp/aws/latest/docs/resources/account_alternate_contact) | resource |
+
+## Inputs
+
+| Name | Description | Type | Default | Required |
+|------|-------------|------|---------|:--------:|
+| <a name="input_account_id"></a> [account\_id](#input\_account\_id) | Target account id where the alternate contacts should be set | `string` | n/a | yes |
+| <a name="input_assume_role_name"></a> [assume\_role\_name](#input\_assume\_role\_name) | The name of the role to assume in target account identified by account\_id | `string` | n/a | yes |
+| <a name="input_aws_partition"></a> [aws\_partition](#input\_aws\_partition) | The AWS partition to use. e.g. aws, aws-cn, aws-us-gov | `string` | `"aws"` | no |
+| <a name="input_billing_contact"></a> [billing\_contact](#input\_billing\_contact) | Billing alternate contact. Set to null to skip. All fields are required when set. | <pre>object({<br/>    name  = string<br/>    title = string<br/>    email = string<br/>    phone = string<br/>  })</pre> | `null` | no |
+| <a name="input_operations_contact"></a> [operations\_contact](#input\_operations\_contact) | Operations alternate contact. Set to null to skip. All fields are required when set. | <pre>object({<br/>    name  = string<br/>    title = string<br/>    email = string<br/>    phone = string<br/>  })</pre> | `null` | no |
+| <a name="input_security_contact"></a> [security\_contact](#input\_security\_contact) | Security alternate contact. Set to null to skip. All fields are required when set. | <pre>object({<br/>    name  = string<br/>    title = string<br/>    email = string<br/>    phone = string<br/>  })</pre> | `null` | no |
+
+## Outputs
+
+| Name | Description |
+|------|-------------|
+| <a name="output_operations_contacts"></a> [operations\_contacts](#output\_operations\_contacts) | Map of configured alternate contact types to their email addresses |
+<!-- END_TF_DOCS -->
diff --git a/modules/aws/alternate-contacts/buildingblock/logo.png b/modules/aws/alternate-contacts/buildingblock/logo.png
new file mode 100644
index 00000000..9cfafbf8
Binary files /dev/null and b/modules/aws/alternate-contacts/buildingblock/logo.png differ
diff --git a/modules/aws/alternate-contacts/buildingblock/main.tf b/modules/aws/alternate-contacts/buildingblock/main.tf
new file mode 100644
index 00000000..40f4d197
--- /dev/null
+++ b/modules/aws/alternate-contacts/buildingblock/main.tf
@@ -0,0 +1,26 @@
+resource "aws_account_alternate_contact" "operations" {
+  alternate_contact_type = "OPERATIONS"
+
+  name          = var.operations_contact.name
+  title         = var.operations_contact.title
+  email_address = var.operations_contact.email
+  phone_number  = var.operations_contact.phone
+}
+
+resource "aws_account_alternate_contact" "billing" {
+  alternate_contact_type = "BILLING"
+
+  name          = var.billing_contact.name
+  title         = var.billing_contact.title
+  email_address = var.billing_contact.email
+  phone_number  = var.billing_contact.phone
+}
+
+resource "aws_account_alternate_contact" "security" {
+  alternate_contact_type = "SECURITY"
+
+  name          = var.security_contact.name
+  title         = var.security_contact.title
+  email_address = var.security_contact.email
+  phone_number  = var.security_contact.phone
+}
diff --git a/modules/aws/alternate-contacts/buildingblock/outputs.tf b/modules/aws/alternate-contacts/buildingblock/outputs.tf
new file mode 100644
index 00000000..52a2fd72
--- /dev/null
+++ b/modules/aws/alternate-contacts/buildingblock/outputs.tf
@@ -0,0 +1,8 @@
+output "operations_contacts" {
+  description = "Map of configured alternate contact types to their email addresses"
+  value = {
+    "operations" = aws_account_alternate_contact.operations.email_address
+    "billing"    = aws_account_alternate_contact.billing.email_address
+    "security"   = aws_account_alternate_contact.security.email_address
+  }
+}
diff --git a/modules/aws/alternate-contacts/buildingblock/provider.tf b/modules/aws/alternate-contacts/buildingblock/provider.tf
new file mode 100644
index 00000000..3fa6bd0f
--- /dev/null
+++ b/modules/aws/alternate-contacts/buildingblock/provider.tf
@@ -0,0 +1,8 @@
+provider "aws" {
+  region = "eu-central-1"
+
+  assume_role {
+    role_arn     = "arn:${var.aws_partition}:iam::${var.account_id}:role/${var.assume_role_name}"
+    session_name = "deploy-alternate-contacts"
+  }
+}
diff --git a/modules/aws/alternate-contacts/buildingblock/variables.tf b/modules/aws/alternate-contacts/buildingblock/variables.tf
new file mode 100644
index 00000000..7b499d0c
--- /dev/null
+++ b/modules/aws/alternate-contacts/buildingblock/variables.tf
@@ -0,0 +1,50 @@
+variable "billing_contact" {
+  type = object({
+    name  = string
+    title = string
+    email = string
+    phone = string
+  })
+  description = "Billing alternate contact. Set to null to skip. All fields are required when set."
+  default     = null
+}
+
+variable "operations_contact" {
+  type = object({
+    name  = string
+    title = string
+    email = string
+    phone = string
+  })
+  description = "Operations alternate contact. Set to null to skip. All fields are required when set."
+  default     = null
+}
+
+variable "security_contact" {
+  type = object({
+    name  = string
+    title = string
+    email = string
+    phone = string
+  })
+  description = "Security alternate contact. Set to null to skip. All fields are required when set."
+  default     = null
+}
+
+// env vars
+
+variable "account_id" {
+  type        = string
+  description = "Target account id where the alternate contacts should be set"
+}
+
+variable "assume_role_name" {
+  type        = string
+  description = "The name of the role to assume in target account identified by account_id"
+}
+
+variable "aws_partition" {
+  type        = string
+  description = "The AWS partition to use. e.g. aws, aws-cn, aws-us-gov"
+  default     = "aws"
+}
diff --git a/modules/aws/alternate-contacts/buildingblock/versions.tf b/modules/aws/alternate-contacts/buildingblock/versions.tf
new file mode 100644
index 00000000..28b0cd98
--- /dev/null
+++ b/modules/aws/alternate-contacts/buildingblock/versions.tf
@@ -0,0 +1,9 @@
+terraform {
+  required_version = ">= 1.3.0"
+  required_providers {
+    aws = {
+      source  = "hashicorp/aws"
+      version = "~> 5.0"
+    }
+  }
+}