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Billy Mainwaring (1941–2019), Welsh international second row rugby union player who played for Aberavon RFC •
Chris Mainwaring (1965–2007), Australian rules footballer and TV presenter •
Daniel Mainwaring (1902–1977), American novelist and screenwriter •
George Mainwaring (1642–1695), English politician •
George Boulton Mainwaring (c. 1773–unknown), British politician •
George Byers Mainwaring (1824–1894), British Indian army officer and linguist •
Henry Mainwaring (1587–1653), English pirate, lawyer, author and diplomat •
John Mainwaring (1724–1807), English theologian and first biographer of the composer Georg Friedrich Händel •
Marion Mainwaring (1922–2015), American novelist •
Matty Mainwaring (b. 1990), English footballer and boxer •
Sam Mainwaring (1841–1907), Welsh socialist and syndicalist trade union activist •
William Mainwaring (1884–1971), British miner and politician •
William Mainwaring (English politician) (1735–1821), English politician, father of George Boulton Mainwaring ==In fiction==