All Saints' Church, also known as Lydd Church or The Cathedral on the Marsh, is a church in Lydd, Kent, South East England. It belongs to the Diocese of Canterbury. All Saints is the longest parish church in Kent at 199 feet (61 m), and also has one of the tallest towers in the county at 132 feet (40 m). The church is thought to incorporate a small Romano-British basilica possibly built in the 5th century, though most of the current fabric is medieval. It was associated with local fraternities or guilds in the 15th century and could seat 1,000 people at a time.