Spinosaurus was named by Stromer (1915). Its type is Spinosaurus aegyptiacus.

It was assigned to Carnosauria by Huene (1923); to Labrosauridae by Nopcsa (1928); to Carnosauria by Kuhn (1939); to Megalosauridae by Romer (1956); to Megalosaurinidae by Swinton (1970); to Carnosauria by Molnar et al. (1990); to Baryonychidae by Rauhut (2003); to Spinosauridae by Stromer (1915), Huene (1926), Huene (1927), Stromer (1934), Stromer (1934), Tatarinov (1964), Walker (1964), Romer (1966), Charig (1967), Maleev (1968), Steel (1970), Molnar (1980), Taquet (1984), Taquet (1984), Chabli (1986), Bonaparte (1986), Bouaziz et al. (1988), Paul (1988), Carroll (1988), Kurzanov (1989), Buffetaut (1989), Molnar (1992), Sereno et al. (1994), Russell (1996), Kellner and Campos (1996), Kellner (1996), Milner (1997), Sereno (1997), Sereno (1998), Taquet and Russell (1998), Sues et al. (2002), Dal Sasso et al. (2005), Candeiro et al. (2006), Ezcurra (2009), Taquet (2010), Buffetaut (2010), Lü et al. (2010), Hendrickx and Mateus (2014), Ibrahim et al. (2017); to Spinosaurini by Arden et al. (2019); and to Spinosaurinae by Sereno et al. (1998), Buffetaut and Ouaja (2002), Holtz et al. (2004), Medeiros (2006), Sánchez-Hernández et al. (2007), Naish and Martill (2007), Kellner et al. (2011), Mateus et al. (2011), Carrano et al. (2012), Ibrahim et al. (2014), Hendrickx et al. (2016), Malafaia et al. (2020), Barker et al. (2021).