The Church of All Saints is the Anglican parish church for the village of Willian in Hertfordshire. It comes under the Diocese of St Albans but is also part of the United Benefice of St Paul's church in nearby Letchworth. The church has been a Grade II* listed building since 1954.
All Saints' dates back to at least Norman times and consists of a nave with two bays and a chancel dating to the 12th and 13th centuries, respectively. The tower and south porch are 15th century. The roof is of Welsh slate with coped gables, while the structure is built of flint and ironstone rubble walls with ashlar dressed stone and buttresses. The tower is of three stages with a stair turret and battlemented parapet and has eight gargoyles.
The 14th and 15th century fenestration is in the Perpendicular style. The church's interior has a 19th century timber barrel roof above both the nave and chancel, while the latter still has its original corbel masks and carved seats. There is a monumental brass to Richard Golden (died 1446) while the walls are adorned with good quality monuments, those in the chancel being to Edward and Joan Lacon (died 1625 and 1624), John Chapman (died 1624) and Thomas Wilson (died 1656). The original 15th century rood screen has been removed.
Buried in the churchyard is Annie Jane Lawrence, who built The Cloisters in nearby Letchworth. Also here are five graves maintained by the Commonwealth War Graves Commission - one from World War I and four from World War II.