The Cathedral Church of the Holy Trinity, Saint Peter, Saint Paul and Saint Swithun, commonly known as Winchester Cathedral, is the cathedral of the city of Winchester, England, and is among the largest of its kind in Northern Europe. The cathedral is the seat of the Bishop of Winchester and is the mother church for the ancient Diocese of Winchester. It is run by a dean and chapter, under the Dean of Winchester.
The cathedral as it stands today was built from 1079 to 1532 and is dedicated to numerous saints, most notably Swithun of Winchester. It has a very long and very wide nave in the Perpendicular Gothic style, an Early English retrochoir, and Norman transepts and tower. With an overall length of , it is the longest medieval cathedral in the world, and only surpassed by the more recent churches of St Peter's Basilica in Rome, Basilica of Our Lady of Peace in Yamoussoukro, Liverpool Anglican Cathedral, Cathedral of St John the Divine in New York City and the Basilica of Our Lady in Aparecida. With an area of , it is also the sixth-largest cathedral by area in the UK, surpassed only by Liverpool, St Paul's, York, Westminster (RC) and Lincoln.
A major tourist attraction, the cathedral attracted 365,000 visitors in 2019, an increase of 12,000 from 2018.
Though churches were recorded in Winchester as early as 164, the first Christian church can be traced back to c. 648, when King Cenwalh of Wessex built a small, cross-shaped building just north of the present building. This building, known as the Old Minster, became the cathedral for the new Diocese of Winchester in 662, a vast area stretching from the English Channel to the River Thames, the bishopric having been transferred from Dorchester on Thames, Oxfordshire by Bishop Wine. The design of this early church cannot be confirmed, for no trace other than ground plan exists today, but Wolstan mentions a gateway tower situated some distance from the west end. Wine died in c. 672, but one of his later successors, Swithun, would become one of the most famous Bishops of Winchester.