File:Stamford, St Martin's church (30137063434).jpg

The church today dates from the late 15th century, although it replaced an earlier building. It is thought that the original church was ruined after the sack of the town in 1461. However, other churches were little damaged, so a more likely reason is that it was neglected by the nuns who owned it at the time. The present church was built in the 1480s.

There is a western tower, clerestoried nave with north and south aisles which clasp the tower, chancel with north and south chapels, and south porch. The church is built in limestone ashlar with lead roofs.

Externally, the nave and chancel have embattled parapets, the windows are late Perpendicular. The tower is of four stages and has an embattled parapet with pinnacles. A spire was intended but never built. The tower is very similar to that of Saint John's church nearby.

The south porch has two storeys, the upper one is now a Chapel, accessible by a narrow spiral stairway.

It is probable that the plan of the nave follows that of the earlier building, as the aisles are fairly narrow. They have arcades of four bays with slim piers and angel corbels holding shields with the Arms of 15th century Bishops of Lincoln. The north aisle at its eastern end terminates at a 19th century arch which was built when the Burghley Chapel was extended. There was a western Gallery in the nave until the late 19th century. The font is octagonal with a window tracery design, from the early 14th century, and is probably from the earlier church.

The chancel was altered with the installation of the tomb of William Cecil in 1598. The north chapel was extended to accommodate his monument. The chancel arch has remains of entrances to a Rood screen which was probably removed in the late 16th century. In 1865 the Burghley Chapel was extended on its north side and a further arch was inserted at the eastern end of the north aisle which blocked the entrance to the Rood loft stairway. The south Chapel is occupied by the organ, but originally housed the Guild of St Martin.

The church has three large monuments, the largest is that to William Cecil, Lord Burghley (1520-1598), once described as "one of the finest examples of its kind in existence", probably by Cornelius Cure. William's parent's monument is located nearby. There is also a large monument to John Cecil, fifth Earl of Exeter and his wife, of white marble with semi-reclining and standing figures either side. There are numerous other wall tablets throughout the church.

The church was refurbished in 1844 by Edward Browning, and has low box pews in the nave. There are further box pews and choir stalls in the chancel which also has geometric patterned tiles.

There are five windows containing reset mediaeval glass including much from Tattershall church. The windows were assembled by Peckitt of York in 1759/60, with several incorporating rather garish patterned glass. The east window is of five lights with reset glass from the second half of the 15th century and Shields from the 16th century.