diff --git a/README.md b/README.md
index 36bd51c..ab0c7f0 100644
--- a/README.md
+++ b/README.md
@@ -20,6 +20,12 @@ Pushes both SHA-tagged and `latest` versions.
 
 **Inputs:** `chart-path`, `version`, `app-version`, `username`, `password`
 
+### `factorio-mod-push`
+Set version, zip, and upload a Factorio mod to mods.factorio.com. Creates README.md if missing. Fails on any API error (auth, unknown mod, invalid release).
+
+**Inputs:** `mod-folder` (default `.`), `version`, `factorio-token`
+**Outputs:** `zip-path`
+
 ### `helm-deploy`
 Deploy via helmbot SSH to vmd127288. Validates all inputs server-side.
 
diff --git a/factorio-mod-push/action.yml b/factorio-mod-push/action.yml
new file mode 100644
index 0000000..2e0d5fa
--- /dev/null
+++ b/factorio-mod-push/action.yml
@@ -0,0 +1,146 @@
+name: Factorio Mod Push
+description: Set version, zip, and upload a Factorio mod to mods.factorio.com
+
+inputs:
+  mod-folder:
+    description: Path to the Factorio mod root directory (containing info.json)
+    required: false
+    default: "."
+  version:
+    description: Semver version string to set in info.json, e.g. 1.0.1
+    required: true
+  factorio-token:
+    description: Factorio API key with ModPortal: Upload Mods permission
+    required: true
+
+outputs:
+  zip-path:
+    description: Absolute path to the generated zip file
+    value: ${{ steps.package.outputs.zip-path }}
+
+runs:
+  using: composite
+  steps:
+    - name: Validate inputs
+      shell: bash
+      run: |
+        MOD_FOLDER="${{ inputs.mod-folder }}"
+        VERSION="${{ inputs.version }}"
+
+        if [ ! -f "$MOD_FOLDER/info.json" ]; then
+          echo "ERROR: info.json not found in $MOD_FOLDER"
+          exit 1
+        fi
+
+        if ! echo "$VERSION" | grep -qE '^[0-9]+\.[0-9]+\.[0-9]+$'; then
+          echo "ERROR: version '$VERSION' does not match semver x.y.z"
+          exit 1
+        fi
+
+    - name: Set version in info.json
+      shell: bash
+      run: |
+        MOD_FOLDER="${{ inputs.mod-folder }}"
+        VERSION="${{ inputs.version }}"
+        sed -i 's/"version": *"[^"]*"/"version": "'"$VERSION"'"/' "$MOD_FOLDER/info.json"
+
+    - name: Create README.md if missing
+      shell: bash
+      run: |
+        MOD_FOLDER="${{ inputs.mod-folder }}"
+        if [ ! -f "$MOD_FOLDER/README.md" ]; then
+          TITLE=$(sed -n 's/.*"title": *"\([^"]*\)".*/\1/p' "$MOD_FOLDER/info.json")
+          DESC=$(sed -n 's/.*"description": *"\([^"]*\)".*/\1/p' "$MOD_FOLDER/info.json")
+          cat > "$MOD_FOLDER/README.md" <<- EOF
+# $TITLE
+
+$DESC
+EOF
+          echo "Created $MOD_FOLDER/README.md"
+        fi
+
+    - name: Read mod name from info.json
+      id: modinfo
+      shell: bash
+      run: |
+        MOD_FOLDER="${{ inputs.mod-folder }}"
+        NAME=$(sed -n 's/.*"name": *"\([^"]*\)".*/\1/p' "$MOD_FOLDER/info.json")
+        echo "name=$NAME" >> $GITHUB_OUTPUT
+
+    - name: Package mod zip
+      id: package
+      shell: bash
+      run: |
+        MOD_FOLDER="${{ inputs.mod-folder }}"
+        NAME=${{ steps.modinfo.outputs.name }}
+        VERSION="${{ inputs.version }}"
+        ZIP_NAME="${NAME}_${VERSION}.zip"
+        ZIP_PATH="${GITHUB_WORKSPACE}/${ZIP_NAME}"
+
+        TMPDIR=$(mktemp -d)
+        cp -r "$MOD_FOLDER/." "$TMPDIR/$NAME/"
+        find "$TMPDIR/$NAME" -type d -name node_modules -exec rm -rf {} + 2>/dev/null || true
+        find "$TMPDIR/$NAME" -type d -name .git -exec rm -rf {} + 2>/dev/null || true
+
+        cd "$TMPDIR"
+        zip -r "$ZIP_PATH" "$NAME/"
+        rm -rf "$TMPDIR"
+
+        echo "zip-path=$ZIP_PATH" >> $GITHUB_OUTPUT
+        echo "Created $ZIP_PATH"
+
+    - name: Init upload to Factorio mod portal
+      id: init
+      shell: bash
+      run: |
+        NAME=${{ steps.modinfo.outputs.name }}
+
+        RESPONSE=$(curl -s -w "\n%{http_code}" \
+          -X POST "https://mods.factorio.com/api/v2/mods/releases/init_upload" \
+          -H "Authorization: Bearer ${{ inputs.factorio-token }}" \
+          -F "mod=$NAME")
+
+        HTTP_CODE=$(echo "$RESPONSE" | tail -n1)
+        BODY=$(echo "$RESPONSE" | sed '$d')
+
+        if [ "$HTTP_CODE" -ne 200 ]; then
+          echo "ERROR: init_upload failed (HTTP $HTTP_CODE)"
+          echo "Response: $BODY"
+          exit 1
+        fi
+
+        UPLOAD_URL=$(echo "$BODY" | sed -n 's/.*"upload_url": *"\([^"]*\)".*/\1/p')
+        if [ -z "$UPLOAD_URL" ]; then
+          echo "ERROR: init_upload failed - no upload_url in response"
+          echo "Response: $BODY"
+          exit 1
+        fi
+
+        echo "upload_url=$UPLOAD_URL" >> $GITHUB_OUTPUT
+
+    - name: Upload zip to Factorio mod portal
+      shell: bash
+      run: |
+        ZIP_PATH=${{ steps.package.outputs.zip-path }}
+        UPLOAD_URL=${{ steps.init.outputs.upload_url }}
+
+        RESPONSE=$(curl -s -w "\n%{http_code}" \
+          -X POST "$UPLOAD_URL" \
+          -F "file=@$ZIP_PATH")
+
+        HTTP_CODE=$(echo "$RESPONSE" | tail -n1)
+        BODY=$(echo "$RESPONSE" | sed '$d')
+
+        if [ "$HTTP_CODE" -ne 200 ]; then
+          echo "ERROR: upload failed (HTTP $HTTP_CODE)"
+          echo "Response: $BODY"
+          exit 1
+        fi
+
+        if ! echo "$BODY" | grep -q '"success": *true'; then
+          echo "ERROR: upload reported failure"
+          echo "Response: $BODY"
+          exit 1
+        fi
+
+        echo "Upload successful: ${{ steps.modinfo.outputs.name }} ${{ inputs.version }}"