diff --git a/.github/workflows/build-fastremap.yml b/.github/workflows/build-fastremap.yml
new file mode 100644
index 000000000..769944a17
--- /dev/null
+++ b/.github/workflows/build-fastremap.yml
@@ -0,0 +1,97 @@
+# SPDX-FileCopyrightText: 2026 The RISE Project
+# SPDX-License-Identifier: MIT
+---
+# Based on: https://github.com/seung-lab/fastremap/blob/1.20.0/.github/workflows/build_wheel.yml
+name: Build fastremap wheels (riscv64)
+
+on:
+  workflow_dispatch:
+    inputs:
+      version:
+        description: 'fastremap version to build (git tag, e.g. 1.20.0)'
+        required: true
+        default: '1.20.0'
+  pull_request:
+    paths:
+      - '.github/workflows/build-fastremap.yml'
+
+concurrency:
+  group: ${{ github.workflow }}-${{ inputs.version || '1.20.0' }}-${{ github.head_ref || github.run_id }}
+  cancel-in-progress: true
+
+permissions:
+  contents: read  # to fetch code (actions/checkout)
+
+env:
+  FASTREMAP_VERSION: ${{ inputs.version || '1.20.0' }}
+  MANYLINUX_RISCV64_IMAGE: quay.io/pypa/manylinux_2_39_riscv64
+
+jobs:
+  setup:
+    uses: $/.github/workflows/_setup.yml
+
+  build_wheels:
+    needs: [setup]
+    name: Build fastremap ${{ inputs.version || '1.20.0' }} ${{ matrix.python }}-manylinux_riscv64
+    runs-on: ubuntu-24.04-riscv
+    timeout-minutes: 60
+    strategy:
+      fail-fast: false
+      matrix:
+        python: [cp312, cp313, cp314, cp314t]
+
+    steps:
+      - name: Checkout fastremap ${{ env.FASTREMAP_VERSION }}
+        uses: actions/checkout@3d3c42e5aac5ba805825da76410c181273ba90b1  # v7.0.1
+        with:
+          repository: seung-lab/fastremap
+          ref: ${{ env.FASTREMAP_VERSION }}
+          persist-credentials: false
+
+      - uses: pypa/cibuildwheel@1828c10ab37f080699c7b81cea34097c684a7074  # v4.2.0
+        with:
+          output-dir: wheelhouse/
+          only: ${{ matrix.python }}-manylinux_riscv64
+        env:
+          CIBW_MANYLINUX_RISCV64_IMAGE: ${{ env.MANYLINUX_RISCV64_IMAGE }}
+          # numpy is a build-time requirement (pyproject.toml's build-system.requires)
+          # and an implicit runtime one (the compiled extension calls numpy's C API at
+          # import time). Only our registry has it for riscv64; only-binary keeps a
+          # newer PyPI release from winning the resolution and compiling from sdist.
+          CIBW_ENVIRONMENT: >-
+            PIP_EXTRA_INDEX_URL=https://pypi.riseproject.dev/simple/
+            PIP_ONLY_BINARY=numpy
+          CIBW_TEST_REQUIRES: pytest numpy
+          # automated_test.py sits next to the unbuilt fastremap/ source package;
+          # staging only the test file keeps that directory out of test_cwd so
+          # `import fastremap` resolves to the installed wheel (gotcha 25).
+          CIBW_TEST_SOURCES: automated_test.py
+          CIBW_TEST_COMMAND: python -m pytest -v automated_test.py
+
+      - name: Check wheel contents
+        run: |
+          python3 - wheelhouse/*.whl <<'EOF'
+          import sys, zipfile
+          names = zipfile.ZipFile(sys.argv[1]).namelist()
+          exts = {n.split("/")[-1].split(".")[0] for n in names if n.endswith(".so")}
+          assert exts == {"fastremap"}, exts
+          licences = {n.rsplit("/", 1)[-1] for n in names if ".dist-info/licenses/" in n} - {""}
+          assert licences == {"LICENSE", "AUTHORS"}, licences
+          EOF
+
+      - name: Store wheels
+        uses: actions/upload-artifact@043fb46d1a93c77aae656e7c1c64a875d1fc6a0a  # v7.0.1
+        with:
+          name: fastremap-${{ env.FASTREMAP_VERSION }}-${{ matrix.python }}-manylinux_riscv64
+          path: ./wheelhouse/*.whl
+          if-no-files-found: error
+
+  publish:
+    name: Publish fastremap ${{ inputs.version || '1.20.0' }}
+    needs: [setup, build_wheels]
+    permissions:
+      contents: write
+      pull-requests: write
+    uses: $/.github/workflows/_publish-wheel.yml
+    with:
+      artifact-pattern: fastremap-${{ inputs.version || '1.20.0' }}-*-manylinux_riscv64