diff --git a/test/check-version-consistency.sh b/test/check-version-consistency.sh
new file mode 100755
index 00000000..84989c4f
--- /dev/null
+++ b/test/check-version-consistency.sh
@@ -0,0 +1,271 @@
+#! /bin/bash
+
+RED='\033[0;31m'
+GREEN='\033[0;32m'
+YELLOW='\033[1;33m'
+NC='\033[0m'
+
+errors=0
+warnings=0
+
+error() {
+    echo -e "${RED}ERROR:${NC} $1"
+    errors=$((errors + 1))
+}
+
+warn() {
+    echo -e "${YELLOW}WARNING:${NC} $1"
+    warnings=$((warnings + 1))
+}
+
+ok() {
+    echo -e "${GREEN}OK:${NC} $1"
+}
+
+# Extract version from configure.ac (source of truth)
+if [ ! -f configure.ac ]; then
+    echo "ERROR: configure.ac not found. Run from repository root."
+    exit 1
+fi
+
+VERSION=$(sed -n 's/^AC_INIT(\[libsodium\],\[\([0-9]*\.[0-9]*\.[0-9]*\)\].*/\1/p' configure.ac)
+MAJOR=$(sed -n 's/^SODIUM_LIBRARY_VERSION_MAJOR=\([0-9]*\)/\1/p' configure.ac)
+MINOR=$(sed -n 's/^SODIUM_LIBRARY_VERSION_MINOR=\([0-9]*\)/\1/p' configure.ac)
+DLL_VERSION=$(sed -n 's/^DLL_VERSION=\([0-9]*\)/\1/p' configure.ac)
+LIBTOOL_VERSION=$(sed -n 's/^SODIUM_LIBRARY_VERSION=\([0-9]*:[0-9]*:[0-9]*\)/\1/p' configure.ac)
+
+if [ -z "$VERSION" ] || [ -z "$MAJOR" ] || [ -z "$MINOR" ]; then
+    echo "ERROR: Could not extract version from configure.ac"
+    exit 1
+fi
+
+echo "Source of truth (configure.ac):"
+echo "  VERSION: $VERSION"
+echo "  SODIUM_LIBRARY_VERSION_MAJOR: $MAJOR"
+echo "  SODIUM_LIBRARY_VERSION_MINOR: $MINOR"
+echo "  DLL_VERSION: $DLL_VERSION"
+echo "  SODIUM_LIBRARY_VERSION (libtool): $LIBTOOL_VERSION"
+echo ""
+
+# Check DLL_VERSION matches MAJOR
+if [ "$DLL_VERSION" != "$MAJOR" ]; then
+    error "DLL_VERSION ($DLL_VERSION) should match SODIUM_LIBRARY_VERSION_MAJOR ($MAJOR)"
+else
+    ok "DLL_VERSION matches MAJOR"
+fi
+
+echo ""
+echo "Checking version files..."
+echo ""
+
+# 1. src/libsodium/include/sodium/version.h
+FILE="src/libsodium/include/sodium/version.h"
+if [ -f "$FILE" ]; then
+    VH_VERSION=$(sed -n 's/.*#define SODIUM_VERSION_STRING "\([0-9]*\.[0-9]*\.[0-9]*\)".*/\1/p' "$FILE")
+    VH_MAJOR=$(sed -n 's/.*#define SODIUM_LIBRARY_VERSION_MAJOR \([0-9]*\).*/\1/p' "$FILE")
+    VH_MINOR=$(sed -n 's/.*#define SODIUM_LIBRARY_VERSION_MINOR \([0-9]*\).*/\1/p' "$FILE")
+
+    if [ "$VH_VERSION" != "$VERSION" ]; then
+        error "$FILE: SODIUM_VERSION_STRING is '$VH_VERSION', expected '$VERSION'"
+    else
+        ok "$FILE: SODIUM_VERSION_STRING"
+    fi
+
+    if [ "$VH_MAJOR" != "$MAJOR" ]; then
+        error "$FILE: SODIUM_LIBRARY_VERSION_MAJOR is '$VH_MAJOR', expected '$MAJOR'"
+    else
+        ok "$FILE: SODIUM_LIBRARY_VERSION_MAJOR"
+    fi
+
+    if [ "$VH_MINOR" != "$MINOR" ]; then
+        error "$FILE: SODIUM_LIBRARY_VERSION_MINOR is '$VH_MINOR', expected '$MINOR'"
+    else
+        ok "$FILE: SODIUM_LIBRARY_VERSION_MINOR"
+    fi
+else
+    warn "$FILE not found (may need to run ./configure first)"
+fi
+
+# 2. builds/msvc/version.h (should be copy of version.h)
+FILE="builds/msvc/version.h"
+if [ -f "$FILE" ]; then
+    MVH_VERSION=$(sed -n 's/.*#define SODIUM_VERSION_STRING "\([0-9]*\.[0-9]*\.[0-9]*\)".*/\1/p' "$FILE")
+    MVH_MAJOR=$(sed -n 's/.*#define SODIUM_LIBRARY_VERSION_MAJOR \([0-9]*\).*/\1/p' "$FILE")
+    MVH_MINOR=$(sed -n 's/.*#define SODIUM_LIBRARY_VERSION_MINOR \([0-9]*\).*/\1/p' "$FILE")
+
+    if [ "$MVH_VERSION" != "$VERSION" ]; then
+        error "$FILE: SODIUM_VERSION_STRING is '$MVH_VERSION', expected '$VERSION'"
+    else
+        ok "$FILE: SODIUM_VERSION_STRING"
+    fi
+
+    if [ "$MVH_MAJOR" != "$MAJOR" ]; then
+        error "$FILE: SODIUM_LIBRARY_VERSION_MAJOR is '$MVH_MAJOR', expected '$MAJOR'"
+    else
+        ok "$FILE: SODIUM_LIBRARY_VERSION_MAJOR"
+    fi
+
+    if [ "$MVH_MINOR" != "$MINOR" ]; then
+        error "$FILE: SODIUM_LIBRARY_VERSION_MINOR is '$MVH_MINOR', expected '$MINOR'"
+    else
+        ok "$FILE: SODIUM_LIBRARY_VERSION_MINOR"
+    fi
+else
+    error "$FILE not found"
+fi
+
+# 3. builds/msvc/resource.rc
+FILE="builds/msvc/resource.rc"
+if [ -f "$FILE" ]; then
+    RC_VERSION=$(sed -n 's/.*#define LIBSODIUM_VERSION_STRING "\([0-9]*\.[0-9]*\.[0-9]*\).*/\1/p' "$FILE")
+    RC_BIN=$(sed -n 's/.*#define LIBSODIUM_VERSION_BIN \([0-9]*,[0-9]*,[0-9]*\).*/\1/p' "$FILE")
+    EXPECTED_BIN=$(echo "$VERSION" | tr '.' ',')
+
+    if [ "$RC_VERSION" != "$VERSION" ]; then
+        error "$FILE: LIBSODIUM_VERSION_STRING is '$RC_VERSION', expected '$VERSION'"
+    else
+        ok "$FILE: LIBSODIUM_VERSION_STRING"
+    fi
+
+    if [ "$RC_BIN" != "$EXPECTED_BIN" ]; then
+        error "$FILE: LIBSODIUM_VERSION_BIN is '$RC_BIN', expected '$EXPECTED_BIN'"
+    else
+        ok "$FILE: LIBSODIUM_VERSION_BIN"
+    fi
+else
+    error "$FILE not found"
+fi
+
+# 4. ci/appveyor/msvc-scripts/process.bat
+FILE="ci/appveyor/msvc-scripts/process.bat"
+if [ -f "$FILE" ]; then
+    BAT_VERSION=$(sed -n 's/.*@VERSION@\/\([0-9]*\.[0-9]*\.[0-9]*\)\/.*/\1/p' "$FILE")
+    BAT_MAJOR=$(sed -n 's/.*@SODIUM_LIBRARY_VERSION_MAJOR@\/\([0-9]*\)\/.*/\1/p' "$FILE")
+    BAT_MINOR=$(sed -n 's/.*@SODIUM_LIBRARY_VERSION_MINOR@\/\([0-9]*\)\/.*/\1/p' "$FILE")
+
+    if [ "$BAT_VERSION" != "$VERSION" ]; then
+        error "$FILE: VERSION is '$BAT_VERSION', expected '$VERSION'"
+    else
+        ok "$FILE: VERSION"
+    fi
+
+    if [ "$BAT_MAJOR" != "$MAJOR" ]; then
+        error "$FILE: MAJOR is '$BAT_MAJOR', expected '$MAJOR'"
+    else
+        ok "$FILE: MAJOR"
+    fi
+
+    if [ "$BAT_MINOR" != "$MINOR" ]; then
+        error "$FILE: MINOR is '$BAT_MINOR', expected '$MINOR'"
+    else
+        ok "$FILE: MINOR"
+    fi
+else
+    error "$FILE not found"
+fi
+
+# 5. appveyor.yml
+FILE="appveyor.yml"
+if [ -f "$FILE" ]; then
+    AV_VERSION=$(sed -n 's/^version: \([0-9]*\.[0-9]*\.[0-9]*\).*/\1/p' "$FILE")
+
+    if [ "$AV_VERSION" != "$VERSION" ]; then
+        error "$FILE: version is '$AV_VERSION', expected '$VERSION'"
+    else
+        ok "$FILE: version"
+    fi
+else
+    error "$FILE not found"
+fi
+
+# 6. dist-build/android-aar.sh
+FILE="dist-build/android-aar.sh"
+if [ -f "$FILE" ]; then
+    AAR_VERSION=$(sed -n 's/^SODIUM_VERSION="\([0-9]*\.[0-9]*\.[0-9]*\).*/\1/p' "$FILE")
+
+    if [ "$AAR_VERSION" != "$VERSION" ]; then
+        error "$FILE: SODIUM_VERSION is '$AAR_VERSION', expected '$VERSION'"
+    else
+        ok "$FILE: SODIUM_VERSION"
+    fi
+else
+    error "$FILE not found"
+fi
+
+# 7. packaging/dotnet-core/libsodium.pkgproj
+FILE="packaging/dotnet-core/libsodium.pkgproj"
+if [ -f "$FILE" ]; then
+    PKG_VERSION=$(sed -n 's/.*<Version>\([0-9]*\.[0-9]*\.[0-9]*\).*/\1/p' "$FILE")
+
+    if [ "$PKG_VERSION" != "$VERSION" ]; then
+        error "$FILE: Version is '$PKG_VERSION', expected '$VERSION'"
+    else
+        ok "$FILE: Version"
+    fi
+else
+    error "$FILE not found"
+fi
+
+# 8. packaging/nuget/package.config (uses 4-part version: X.Y.Z.0)
+FILE="packaging/nuget/package.config"
+if [ -f "$FILE" ]; then
+    NUGET_VERSION=$(sed -n 's/.*version *= *"\([0-9]*\.[0-9]*\.[0-9]*\).*/\1/p' "$FILE")
+    NUGET_PATHVER=$(sed -n 's/.*pathversion="\([0-9_]*\)".*/\1/p' "$FILE")
+    EXPECTED_PATHVER="${VERSION}_0"
+    EXPECTED_PATHVER=$(echo "$EXPECTED_PATHVER" | tr '.' '_')
+
+    if [ "$NUGET_VERSION" != "$VERSION" ]; then
+        error "$FILE: version is '$NUGET_VERSION', expected '$VERSION'"
+    else
+        ok "$FILE: version"
+    fi
+
+    if [ "$NUGET_PATHVER" != "$EXPECTED_PATHVER" ]; then
+        error "$FILE: pathversion is '$NUGET_PATHVER', expected '$EXPECTED_PATHVER'"
+    else
+        ok "$FILE: pathversion"
+    fi
+else
+    error "$FILE not found"
+fi
+
+# 9. configure (generated from configure.ac)
+FILE="configure"
+if [ -f "$FILE" ]; then
+    CONF_VERSION=$(sed -n "s/^PACKAGE_VERSION='\([0-9]*\.[0-9]*\.[0-9]*\)'/\1/p" "$FILE")
+    CONF_MAJOR=$(sed -n 's/^SODIUM_LIBRARY_VERSION_MAJOR=\([0-9]*\)/\1/p' "$FILE")
+    CONF_MINOR=$(sed -n 's/^SODIUM_LIBRARY_VERSION_MINOR=\([0-9]*\)/\1/p' "$FILE")
+
+    if [ "$CONF_VERSION" != "$VERSION" ]; then
+        error "$FILE: PACKAGE_VERSION is '$CONF_VERSION', expected '$VERSION' (run ./autogen.sh)"
+    else
+        ok "$FILE: PACKAGE_VERSION"
+    fi
+
+    if [ "$CONF_MAJOR" != "$MAJOR" ]; then
+        error "$FILE: SODIUM_LIBRARY_VERSION_MAJOR is '$CONF_MAJOR', expected '$MAJOR' (run ./autogen.sh)"
+    else
+        ok "$FILE: SODIUM_LIBRARY_VERSION_MAJOR"
+    fi
+
+    if [ "$CONF_MINOR" != "$MINOR" ]; then
+        error "$FILE: SODIUM_LIBRARY_VERSION_MINOR is '$CONF_MINOR', expected '$MINOR' (run ./autogen.sh)"
+    else
+        ok "$FILE: SODIUM_LIBRARY_VERSION_MINOR"
+    fi
+else
+    warn "$FILE not found (run ./autogen.sh to generate)"
+fi
+
+echo ""
+echo "=========================================="
+if [ $errors -gt 0 ]; then
+    echo -e "${RED}FAILED:${NC} $errors error(s), $warnings warning(s)"
+    exit 1
+elif [ $warnings -gt 0 ]; then
+    echo -e "${YELLOW}PASSED WITH WARNINGS:${NC} $warnings warning(s)"
+    exit 0
+else
+    echo -e "${GREEN}PASSED:${NC} All version checks passed"
+    exit 0
+fi