Karl Alexander may refer to:
Karl Alexander, Duke of Württemberg (1684–1737), who served as Duke from 1698 until 1737 Karl Alexander, 5th Prince of Thurn and Taxis (1770–1827), the 5th Prince of Thurn and Taxis Karl Alexander, Grand Duke of Saxe-Weimar-Eisenach (1818–1901), who served as Grand Duke from 1853 to 1901 Karl-Alexander Island, also known as Zemlya Karla-Alexandra Karl Alexander (writer) (1938–2015), American writer and author of Time After Time
See also: Christian Frederick Charles Alexander, Margrave of Brandenburg-Ansbach (1736–1806), commonly known as Karl Alexander Karl Alexander Müller (1927–2023), Swiss physicist and Nobel laureate Carl Alexander Heideloff (1789–1865), German architect