diff --git a/tests/test_a11y_r1_password_toggle.py b/tests/test_a11y_r1_password_toggle.py
new file mode 100644
index 00000000..901cae0b
--- /dev/null
+++ b/tests/test_a11y_r1_password_toggle.py
@@ -0,0 +1,115 @@
+#!/usr/bin/env python3
+"""
+Smoke test: a11y R1 password visibility toggle exists and is correctly structured.
+Issue #551: [a11y] R1: Add password visibility toggle on login
+
+Verifies that deploy/gitea-a11y/custom/templates/user/auth/signin_inner.tmpl
+contains all required elements for an accessible password toggle:
+- password input with type="password" and proper id/name
+- toggle button with id="toggle-password", aria-label, title, and onclick
+- JavaScript function togglePasswordVisibility() that toggles type and aria-label
+"""
+
+import sys
+from pathlib import Path
+
+# Resolve repo root
+REPO_ROOT = Path(__file__).resolve().parent.parent
+TEMPLATE_PATH = REPO_ROOT / "deploy" / "gitea-a11y" / "custom" / "templates" / "user" / "auth" / "signin_inner.tmpl"
+
+
+def test_r1_toggle_button_exists():
+    """Template contains the toggle button with required attributes."""
+    content = TEMPLATE_PATH.read_text()
+
+    # Check button exists with proper ID
+    assert 'id="toggle-password"' in content, "Toggle button missing id='toggle-password'"
+
+    # Check button has type="button"
+    assert 'type="button"' in content, "Toggle button missing type='button'"
+
+    # Check aria-label (initially "Show password")
+    assert 'aria-label="Show password"' in content, "Toggle button missing initial aria-label='Show password'"
+
+    # Check title attribute
+    assert 'title="Show password"' in content, "Toggle button missing initial title='Show password'"
+
+    # Check onclick calls togglePasswordVisibility()
+    assert 'onclick="togglePasswordVisibility()"' in content, "Toggle button missing onclick handler"
+
+    print("✓ Toggle button exists with required attributes")
+
+
+def test_r1_password_input_exists():
+    """Template contains password input with proper id and type."""
+    content = TEMPLATE_PATH.read_text()
+
+    # Check password input id and name
+    assert 'id="password"' in content, "Password input missing id='password'"
+    assert 'name="password"' in content, "Password input missing name='password'"
+
+    # Check type is "password"
+    assert 'type="password"' in content, "Password input missing type='password'"
+
+    # Check required and aria-required for a11y
+    assert 'required' in content, "Password input missing required attribute"
+    assert 'aria-required="true"' in content, "Password input missing aria-required='true'"
+
+    print("✓ Password input exists with type='password' and required a11y")
+
+
+def test_r1_javascript_function_exists():
+    """Template contains togglePasswordVisibility JS function."""
+    content = TEMPLATE_PATH.read_text()
+
+    # Function definition
+    assert 'function togglePasswordVisibility()' in content, "Missing togglePasswordVisibility function"
+
+    # Function toggles input.type
+    assert "input.type = 'text'" in content, "Function doesn't set input.type to 'text'"
+    assert "input.type = 'password'" in content, "Function doesn't reset input.type to 'password'"
+
+    # Function updates aria-label
+    assert "'Hide password'" in content, "Function doesn't update aria-label to 'Hide password'"
+    assert "'Show password'" in content, "Function doesn't update aria-label back to 'Show password'"
+
+    # Function updates button textContent (emoji)
+    assert "btn.textContent = '🙈'" in content, "Function missing hide emoji"
+    assert "btn.textContent = '👁'" in content, "Function missing show emoji"
+
+    print("✓ JavaScript toggle function correctly implemented")
+
+
+def test_r1_label_association():
+    """Password field has associated label."""
+    content = TEMPLATE_PATH.read_text()
+
+    # Label for attribute matches input id
+    assert 'for="password"' in content, "Label missing for='password'"
+    assert 'id="password"' in content, "Input missing id='password'"
+
+    print("✓ Label correctly associated with password input")
+
+
+def run_all():
+    """Run all R1 checks."""
+    print("R1 Smoke Test — Password Visibility Toggle (issue #551)")
+    print("-" * 60)
+    try:
+        test_r1_toggle_button_exists()
+        test_r1_password_input_exists()
+        test_r1_javascript_function_exists()
+        test_r1_label_association()
+        print("-" * 60)
+        print("✅ All R1 checks passed")
+        return 0
+    except AssertionError as e:
+        print(f"\n❌ R1 check failed: {e}")
+        return 1
+    except Exception as e:
+        print(f"\n❌ Unexpected error: {e}")
+        return 1
+
+
+if __name__ == "__main__":
+    sys.exit(run_all())