Baggio Old Church, Architectural ensemble and church building in Baggio district, Milan, Italy.

The Chiesa Vecchia di Sant'Apollinare, known in Lombard as Gesa Veggia, is the oldest church in Baggio, a district of Milan. Rebuilt in the late 19th century, it retains its original 10th-century bell tower, built with materials and in an architectural style datable to that period. It stands on via Ceriani next to the Palazziètt, near the piazzetta del Moronasc and the Cascina Monastero.

The church was built by the da Baggio family between the 10th and 11th centuries and stood under their patronage; its bell tower is datable to the 10th century by style and materials. It is first documented in 1161, in a deed of the provost of Cesano concerning a land purchase. In 1398 the Notitia cleri listed it among the richest churches of the Pieve di Cesano Boscone. On 26 April 1628 Anselmo IV Baggio granted the establishment of a parish in his property, and on 8 September 55 heads of household met in the church cemetery.

The church is dedicated to Saint Apollinaris, but locals call it Gesa Veggia in Lombard. In 1604 Cardinal Federico Borromeo noted a wooden tabernacle and a pulpit often used by Jesuit preachers. The Confraternita del Santissimo Sacramento, Baggio's first association, kept a candle burning by the tabernacle.

The old church stands in the centre of Baggio on via Ceriani, beside the Palazziètt and near the piazzetta del Moronasc and Cascina Monastero. The bell tower is the only part that survived the late-19th-century rebuilding, so look for it to recognise the medieval structure. The building is still a consecrated church, so visits should respect its use for worship.

The Milanese saying "andà a Bagg a sonà l'òrghen" (go to Baggio to play the organ) mocks a church that long had no organ, only a wall painting of one. An organ was installed during the late-19th-century rebuilding, so the joke's original target is now hard to verify.