diff --git a/conditional-variables/action.yaml b/conditional-variables/action.yaml
new file mode 100644
index 0000000..a1898ea
--- /dev/null
+++ b/conditional-variables/action.yaml
@@ -0,0 +1,45 @@
+name: Conditional Variables
+
+description: |
+  Evaluates a list of conditions and exposes variables as outputs.
+  Conditions are evaluated in order. All matching conditions are applied.
+  If multiple conditions set the same variable, the last matching value wins.
+
+inputs:
+  context:
+    description: |
+      Context variables available during condition evaluation.
+
+  conditions:
+    description: |
+      List of conditions to evaluate.
+
+      Example:
+
+        - when:
+            branch:
+              - 9.0-alpine-24
+              - 9.0-alpine-23
+          set:
+            DOTNET_VERSION: 9.0
+
+    required: true
+
+  fail-on-no-match:
+    description: |
+      Fail the action when no condition matches.
+    required: false
+    default: "false"
+
+runs:
+  using: composite
+
+  steps:
+    - name: Evaluate conditions
+      shell: bash
+      env:
+        CONTEXT: ${{ inputs.context }}
+        CONDITIONS: ${{ inputs.conditions }}
+        FAIL_ON_NO_MATCH: ${{ inputs.fail-on-no-match }}
+      run: |
+        "${{ github.action_path }}/evaluate.sh"
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diff --git a/conditional-variables/evaluate.sh b/conditional-variables/evaluate.sh
new file mode 100644
index 0000000..894eb2d
--- /dev/null
+++ b/conditional-variables/evaluate.sh
@@ -0,0 +1,141 @@
+trim() {
+    local var="$*"
+    var="${var#"${var%%[![:space:]]*}"}"
+    var="${var%"${var##*[![:space:]]}"}"
+    printf '%s' "$var"
+}
+
+declare -A context
+
+#
+# Load context
+#
+while IFS='=' read -r key value; do
+
+    key="$(trim "${key:-}")"
+    value="$(trim "${value:-}")"
+
+    [[ -z "$key" ]] && continue
+    [[ "$key" =~ ^# ]] && continue
+
+    context["$key"]="$value"
+
+done <<< "$CONTEXT"
+
+matched=false
+
+#
+# Evaluate conditions (OR)
+#
+while IFS= read -r condition; do
+
+    condition="$(trim "${condition:-}")"
+
+    [[ -z "$condition" ]] && continue
+    [[ "$condition" =~ ^# ]] && continue
+
+    read -r variable operator expected <<< "$condition"
+
+    #
+    # Validate condition format
+    #
+    if [[ -z "${variable:-}" || -z "${operator:-}" || -z "${expected:-}" ]]; then
+        echo "Invalid condition: $condition"
+        exit 1
+    fi
+
+    if [[ ! -v context["$variable"] ]]; then
+        echo "Unknown context variable '$variable'"
+        exit 1
+    fi
+
+    actual="${context[$variable]}"
+
+    case "$operator" in
+
+        "==")
+            [[ "$actual" == "$expected" ]] && matched=true
+            ;;
+
+        "!=")
+            [[ "$actual" != "$expected" ]] && matched=true
+            ;;
+
+        ">"|">="|"<"|"<=")
+
+            #
+            # Numeric comparisons only
+            #
+            if [[ ! "$actual" =~ ^-?[0-9]+$ ]]; then
+                echo "Numeric operator '$operator' requires integer value. Actual: '$actual'"
+                exit 1
+            fi
+
+            if [[ ! "$expected" =~ ^-?[0-9]+$ ]]; then
+                echo "Numeric operator '$operator' requires integer comparison value. Expected: '$expected'"
+                exit 1
+            fi
+
+            case "$operator" in
+                ">")
+                    (( actual > expected )) && matched=true
+                    ;;
+                ">=")
+                    (( actual >= expected )) && matched=true
+                    ;;
+                "<")
+                    (( actual < expected )) && matched=true
+                    ;;
+                "<=")
+                    (( actual <= expected )) && matched=true
+                    ;;
+            esac
+            ;;
+
+        *)
+            echo "Unsupported operator: $operator"
+            exit 1
+            ;;
+
+    esac
+
+    #
+    # OR logic:
+    # stop at first match
+    #
+    [[ "$matched" == true ]] && break
+
+done <<< "$CONDITIONS"
+
+#
+# Set outputs
+#
+if [[ "$matched" == true ]]; then
+
+    while IFS= read -r output; do
+
+        output="$(trim "${output:-}")"
+
+        [[ -z "$output" ]] && continue
+        [[ "$output" =~ ^# ]] && continue
+
+        #
+        # Validate output syntax
+        #
+        if [[ ! "$output" =~ ^[A-Za-z_][A-Za-z0-9_]*= ]]; then
+            echo "Invalid variable definition: $output"
+            exit 1
+        fi
+
+        echo "$output" >> "$GITHUB_OUTPUT"
+
+    done <<< "$VARIABLES"
+
+fi
+
+if [[ "$matched" == false && "$FAIL_ON_NO_MATCH" == "true" ]]; then
+    echo "No conditions matched"
+    exit 1
+fi
+
+echo "matched=$matched" >> "$GITHUB_OUTPUT"
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