Drupal is the third popular Content Management System. Drupal has very many free themes that you can choose from depending on the site you are designing. You can get free Drupal themes from the following websites:
Those are just some of the sites where you can download the free Drupal theme. The Drupal free themes list over 1200 Drupal 7 and Drupal 8 themes. These themes are fetched from drupal.org and they have a better filter option. There are various categories such as Admin theme, base theme, blog, Corporate and finance, e-commerce, education, entertainment, hotel, magazine and news, real estate, sports, technology among many others.
Drupal Education theme