Abu Ja'far Ahmad ibn Yusuf ibn Ibrahim ibn Tammam al-Siddiq Al-Baghdadi (Arabic: أبو جعفر أحمد بن يوسف بن ابراهيم بن تمام الصديق البغدادي; 835–912), known in the West by his Latinized name Hametus, was a Muslim Arab mathematician, like his father Yusuf ibn Ibrahim (Arabic: يوسف بن ابراهيم الصدَيق البغدادي).