Sizer may refer to:
People Josephine E. Sizer (1862-1937), American temperance reformer Stephen Sizer (born 1953), English author on Judeo-Christian topics Ted Sizer (1932–2009), founder of the Essential school movement Theodore Sizer (art historian) (1892–1967), American art historian, author
Places Mount Sizer, prominent peak located on Blue Ridge in Henry W. Coe State Park in California
Other Sizer Barker, indie band from Liverpool, England