Omeisaurus was named by Young (1939).

It was assigned to Helopodinae by Young (1939); to Sauropoda by Huene (1958); to Astrodontidae by Young (1958) and Huene (1959); to Brachiosauridae by Tatarinov (1964) and Romer (1966); to Camarasauridae by Rozhdestvensky (1977); to Cetiosauridae by McIntosh (1990); to Shunosaurinae by McIntosh (1990); to Mamenchisaurinae by Dong (1992); to Sauropoda by Calvo and Salgado (1995); to Euhelopodinae by Romer (1956), Steel (1970), Swinton (1970), Dong et al. (1983), Dong (1990) and Martin-Rolland (1999); to Euhelopodidae by Carroll (1988), Upchurch (1995), Upchurch (1995), Buffetaut et al. (1995), Vickaryous and Ryan (1997), Buffetaut et al. (2002), Buffetaut et al. (2006), Royo-Torres et al. (2006) and Lü et al. (2006); to Omeisauridae by Wilson (2002) and Allain and Aquesbi (2008); to Eusauropoda by Sereno (1997), Sereno (1998), Wilson and Sereno (1998), Sereno (1999), Sereno et al. (1999), Upchurch et al. (2004), Upchurch et al. (2007), Ksepka and Norell (2010), Sekiya (2011), D'Emic (2012), Otero and Pol (2013), Apaldetti et al. (2013) and Mocho et al. (2014); and to Mamenchisauridae by He et al. (1984), He (1984), He et al. (1988), Zhang and Chen (1996), Dong (1997), McIntosh (1997), Dong (1998), Tang et al. (2001), Peng et al. (2005), Naish and Martill (2007), Ye et al. (2007), Suteethorn et al. (2010), Li et al. (2010), Jiang et al. (2011), Li et al. (2011), Suteethorn et al. (2013), Ren et al. (2018) and Tan et al. (2019).