St Paul's Cathedral, formally the Cathedral Church of St Paul the Apostle, is an Anglican cathedral in London, England, the seat of the Bishop of London. The cathedral serves as the mother church of the Diocese of London. It is on Ludgate Hill at the highest point of the City of London. Its dedication in honour of Paul the Apostle dates back to the original church on this site, founded in AD 604. The high-domed present structure, which was completed in 1710, is a Grade I listed building that was designed in the English Baroque style by Sir Christopher Wren. The cathedral's reconstruction was part of a major rebuilding programme initiated in the aftermath of the Great Fire of London. The earlier Gothic cathedral (Old St Paul's Cathedral), largely destroyed in the Great Fire, was a central focus for medieval and early modern London, including Paul's walk and St Paul's Churchyard, being the site of St Paul's Cross.

The cathedral is one of the most famous and recognisable sights of London. Its dome, surrounded by the spires of Wren's City churches, has dominated the skyline for over 300 years. At 365 ft (111 m) high, it was the tallest building in London from 1710 to 1963. The dome is still one of the highest in the world. St Paul's is the second-largest church building in area in the United Kingdom, after Liverpool Cathedral.

Services held at St Paul's have included the funerals of Admiral Lord Nelson, the Duke of Wellington, Winston Churchill and Margaret Thatcher; jubilee celebrations for Queen Victoria; an inauguration service for the Metropolitan Hospital Sunday Fund; peace services marking the end of the First and Second World Wars; the wedding of Prince Charles and Lady Diana Spencer; the launch of the Festival of Britain; and the thanksgiving services for the Silver, Golden, Diamond, and Platinum Jubilees and the 80th and 90th birthdays of Queen Elizabeth II. St Paul's Cathedral is the central subject of much promotional material, as well as of images of the dome surrounded by the smoke and fire of the Blitz. The cathedral is a working church with hourly prayer and daily services. The tourist entry fee at the door is £25 for adults (January 2024) but no charges are made to worshippers attending services, or for private prayer.

The nearest London Underground station is St Paul's, which is 130 yards (120 m) away from St Paul's Cathedral.