The San Pelayo chapel (Basque: San Pelaio baseliza or Doneperai baseliza) is a Romanesque chapel located in Bakio, Bizkaia, very close to San Juan de Gaztelugatxe. Situated along the coastal route connecting Bakio with Bermeo, it stands as one of the oldest preserved Christian structures in Bizkaia, alongside San Pedro de Abrisketa in Arrigorriaga and San Miguel de Zumetxaga chapel in Mungia.

Dating back to the 12th century, this modest-sized building has retained its original rectangular floor plan despite the passage of time and various interventions. Constructed with masonry walls and ashlar cornerstones, the chapel features a single rectangular nave and a smaller square apse. The transition from the nave to the apse is marked by a slightly pointed triumphal arch with double archivolts. The structure is topped with a gabled roof, and a tower with a hipped roof rises at the western end. A sacristy, added later, adjoins the apse and utilizes the coverage of the perimeter portico, which was also added after the original construction.

Notable architectural elements include the main entrance and the apse window. The entrance features a slightly pointed, splayed arch with three exterior archivolts resting on imposts supported by engaged columns with cubic bases and truncated pyramidal capitals. The apse window is deeply splayed, with a semicircular arch flanked by two engaged columns adorned with decorated shafts.

The San Pelayo chapel is a significant example of Romanesque architecture in the Basque Country, offering insight into the region’s medieval ecclesiastical design and construction techniques.