Haci Alaeddin is an architect from Konya who built the Old Mosque of Edirne at the beginning of the 15th century with his assistant builder Ömer bin Ibrahim. Their contribution is acknowledged on the inscriptive plaque (kitabe) above the western portal of the Old Mosque.
Source: AYVERDI, Ekrem Hakki. Osmanli mi'marisinde Çelebi ve II. Sultan Murad Devri 806-855 (1403-1451): II. Baha Matbaasi: Istanbul, 1972.