church in the London borough of Westminster (Westminster, City of), since 1614 the official church of the House of Commons (Commons, House of). It stands near Westminster Abbey and the Houses of Parliament (Parliament, Houses of).

The church was founded by the abbot of Westminster in the early or mid-12th century, but the original structure was demolished in the 14th century. Between 1486 and 1523 it was rebuilt, and galleries were added in 1641 and 1681. Further alterations were made in subsequent periods, including extensive repairs after the bombing raids that devastated London in World War II. The 16th-century east window is a distinctive characteristic of the church. Among the notables married in St. Margaret's were the diarist Samuel Pepys (Pepys, Samuel) (in 1655), the poet John Milton (Milton, John) (1656), and the statesman Winston Churchill (Churchill, Sir Winston) (1908). St. Margaret's Church, Westminster Abbey, and the Houses of Parliament were collectively designated a UNESCO World Heritage site in 1987.