Custom Login Redirect: Use built-in WordPress hooks to redirect people to your custom login page when wp-login.php gets called

redirect_login_page.php

<?php // Ignore this first line when copying to your child theme's functions.php file.

/**
 * Redirects wp-login.php to your custom login page.
 */
function redirect_login_page() {
  $login_page  = home_url( '/my-custom-login-page/' );
  $page_viewed = basename($_SERVER['REQUEST_URI']);
 
  if( $page_viewed == "wp-login.php" && $_SERVER['REQUEST_METHOD'] == 'GET' ) {
    wp_redirect( $login_page );
    exit;
  }
}
add_action( 'init','redirect_login_page' );

wordpress_custom_login_url.php

<?php // Ignore this first line when copying to your child theme's functions.php file.

/**
 * Filters the login URL.
 *
 * Example adapted from https://developer.wordpress.org/reference/hooks/login_url/
 *
 * @since 2.8.0
 * @since 4.2.0 The `$force_reauth` parameter was added.
 *
 * @param string $login_url    The login URL. Not HTML-encoded.
 * @param string $redirect     The path to redirect to on login, if supplied.
 * @param bool   $force_reauth Whether to force reauthorization, even if a cookie is present.
 *
 * @return string
 */
function wordpress_custom_login_url( $login_url, $redirect, $force_reauth ) {
    // This will append your custom login page's path to you main site URL (e.g. https://domain.com/custom-login/)
    $login_url = site_url( '/my-custom-login-page/', 'login' ); // Change to your path.
    if ( ! empty( $redirect ) ) {
        $login_url = add_query_arg( 'redirect_to', urlencode( $redirect ), $login_url );
    }
    if ( $force_reauth ) {
        $login_url = add_query_arg( 'reauth', '1', $login_url );
    }
    return $login_url;
}
add_filter( 'login_url', 'wordpress_custom_login_url', 10, 3 );