Mosasauria was named as an order. It was considered monophyletic by Gauthier et al. (2012).

It was corrected as Mosasauri by Gadow (1898) and Jaekel (1910); it was synonymized subjectively with Pythonomorpha by Hay (1902); it was reranked as the suborder Mosasauria by Osborn (1903); it was reranked as the suborder Mosasauri by Jaekel (1911); it was reranked as the superfamily Mosasauria by Kuhn (1946) and Reeder et al. (2015); it was reranked as the superfamily Mosasauroidea by Caldwell et al. (1995), Bardet et al. (2003), Schulp et al. (2004), Bell and Polcyn (2005), Schulp et al. (2008), Gauthier et al. (2012), Pyron et al. (2013), Bell et al. (2013), Garcia et al. (2015), Frey et al. (2016) and Hornung et al. (2018).

It was assigned to Reptilia by Leidy (1873); to Squamata by Osborn (1903) and Osborn (1904); to Lyognatha by Jaekel (1910); to Lyognathi by Jaekel (1911); to Pythonomorpha by Gadow (1898) and Perrier (1928); to Lacertilia by Kuhn (1946); to Anguimorpha by Caldwell et al. (1995); to Squamata by Bardet et al. (2003); to Toxicofera by Pyron et al. (2013) and Reeder et al. (2015); and to Squamata by Osborn (1903), Schulp et al. (2004), Bell and Polcyn (2005), Schulp et al. (2008), Gauthier et al. (2012), Bell et al. (2013), Garcia et al. (2015), Frey et al. (2016) and Hornung et al. (2018).