Sidi Belahcen Mosque, also known as Sidi Bel Hasan Mosque or Sidi Abu al-Hasan Mosque is a historic mosque in the city of Tlemcen, Algeria. The mosque is located in the southwest of the square, next to the Great Mosque of Tlemcen. Today it serves as the Islamic Calligraphy Museum of Tlemcen.

Compared to other mosques from the same period, this mosque is fairly understated in design. The floor and qibla wall of the mosque are covered in identical tiles, and there is no sahn. It was the first of its kind in Algeria and precedes by three or four centuries the style used in the Andalusian Moorish architecture. The ceiling was composed of interlocking cedar tree planks.