McWilliams is a surname. Notable people with the surname include:

• Alfred McWilliams (1844–1928), Canadian politician from Prince Edward Island
• Bill McWilliams (1910–1997), American baseball player
• Brendan McWilliams (1944–2007), Irish meteorologist and science writer
• Carey McWilliams (journalist) (1905–1980), American author, editor, and lawyer
• Carey McWilliams (marksman) (b. 1973), American author, marksman, and skydiver
• Caroline McWilliams (1945–2010), American television actress; former wife of Michael Keaton
• Christopher 'Crip' McWilliams (1963–2008), Irish nationalist; convicted of the murder of the LVF leader Billy Wright
• Cynthia Kaye McWilliams (contemporary), American actress
• David McWilliams (American football) (contemporary), American college football coach
• David McWilliams (economics pundit) (b. 1966), Irish economist, commentator, and author
• David McWilliams (musician) (1945–2002), Northern Irish singer, songwriter, and guitarist
• Derek McWilliams (b. 1966), Scottish football player
• Douglas McWilliams (born 1951), British economist
• Edmund McWilliams (contemporary), American diplomat and ambassador
• Elsie McWilliams (1896–1985), American songwriter
• Eric McWilliams (b. 1950), American basketball player
• Fleming McWilliams (contemporary), American singer and songwriter
• Francis McWilliams (1926–2022), Scottish engineer and Lord Mayor of London
• George McWilliams (1865–1907), Australian doctor and MP
• Jackie McWilliams (b. 1964), Irish Olympic field hockey player
• Jelena McWilliams (b. 1973), U.S. banker, nominee to lead Federal Deposit Insurance Corporation (FDIC)
• Jeremy McWilliams (b. 1964), Irish motorcycle road racer
• Joe McWilliams (1904–1996), American inventor, industrial engineer, and nationalist
• John D. McWilliams (1891–1975), American politician from Connecticut; U.S. Representative 1943–45
• Johnny McWilliams (b. 1972), American football player
• Julia Carolyn McWilliams, birth name of American cooking teacher, author, and television personality Julia Child
• Larry McWilliams (b. 1954), American baseball player
• Monica McWilliams (b. 1954), Northern Ireland academic and politician
• Nancy McWilliams, American psychoanalyst and writer
• Peter McWilliams (1949–2000), American marijuana activist and writer
• Rhys McWilliams (b. 1985), English ice hockey player
• Roland Fairbairn McWilliams (1874–1957), Canadian politician from Manitoba
• Ruben McWilliams (1901–1984), New Zealand rugby player
• Shorty McWilliams (1926–1997), American football player
• Taj McWilliams-Franklin (b. 1970), American women’s basketball player
• Taylor McWilliams (born 1980/1981), American real estate developer
• William McWilliams (1856–1929), Australian politician from Tasmania
• Wilson Carey McWilliams (1933–2005), American political scientist and writer

• Lally McWilliams, a fictional character in the anime Gundam SEED DESTINY