The Fuentidueña Apse is a Romanesque apse dated 1175–1200 that was built as part of the San Martín Church at Fuentidueña, province of Segovia, Castile and León, Spain. Little is known about the church's commission, design or early history. It is believed to have been built when the town was of strategic importance to the Christian kings of Castile in their defence against Moorish invaders; the church is situated on an imposing hill below a fortified castle.