Elenska Basilica, Early Christian church ruins near Pirdop, Bulgaria.

The Elenska Basilica is an early Christian church ruin located near the town of Pirdop in central Bulgaria. The building had three naves, a central dome and apses at both ends, combining two architectural approaches in a single structure.

The basilica was built towards the end of the 5th century and rebuilt under Emperor Justinian I (527–565), who had a dome added to the originally domeless church. It served as an active monastery and literary centre during the Second Bulgarian Empire. Around 1700 the Ottoman forces of Yahya Pasha bombarded and burned it, and it was abandoned.

The name comes from the Elenska River, which flows by the ruins, not from a river called Elena. Thracologist Alexander Fol linked the area's name to a legend of a deer descending from the Balkan Mountains each year to be sacrificed; many deer bones have been found nearby. Another theory derives it from "elini", the Bulgarianized word for Greeks. A 13th-century Middle Bulgarian manuscript, the Pirdop Acts of the Apostles, may have been written at the monastery.

The ruins sit outside Pirdop and can be reached on foot from the town center. The ground is uneven in places and some passages between the walls are narrow, so sturdy footwear is a good idea.

Finds from the site show that a sanctuary already existed here long before the basilica was built, suggesting this spot was considered sacred across many different eras. Alongside the church itself, traces of residential and defensive buildings were also uncovered, pointing to a wider complex that went well beyond a simple place of worship.