The surname Mainwaring (/ˈmænərɪŋ/ or /ˌmeɪnˈwɛərɪŋ/) is an Anglo-Norman territorial surname deriving from "Mesnil Warin" (or "Mesnilwarin", "Mesnilvarin", "Mesnil Varin"), from the village of Le Mesnil Varin (= "the manor of Warin"), now Saint-Paër, Normandy.

Notable people with the surname include:

People

• 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
• Greg Manwaring (b. 1962), Classical animator, director, member of the Academy of Motion Pictures Arts and Sciences
• Lieutenant-Colonel Harry Mainwaring (1919–2014), who was awarded an MC in fierce fighting after D-Day in the Normandy Campaign
• Henry Mainwaring (c. 1586-1653), 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
• Ranulph Mainwaring, Justice of Chester in the reign of Richard I (1189–1199)
• Sam Mainwaring, Jr., labor activist in Britain, South Africa and the United States; nephew of Sam Mainwaring

In fiction

• Captain George Mainwaring, commander of the Home Guard platoon in the BBC sitcom Dad's Army

• Elizabeth Mainwaring, Captain Mainwaring's wife
• Barry Mainwaring, Captain Mainwaring's long-lost brother

• Lil Mainwaring, In Movie "Marnie" - Alfred Hitcock's movie - Sean Connery's Main Line Philadelphia former sister in law
• Veronica Mainwaring, Protagonist in Demon Lover, 1929 novel by Dion Fortune

Transportation

• Mainwaring (HBC vessel), operated by the HBC from 1807-1820, see Hudson's Bay Company vessels