The bigmouth sanddab (Citharichthys gilberti) is a species of flatfish in the large-tooth flounder family Paralichthyidae. It is native to the eastern Pacific Ocean, in tropical waters ranging from the Gulf of California in the north to Peru in the south. It occurs in shallow waters off the coast, to a maximum depth of 36 m (118 ft). This demersal fish inhabits the soft bottoms of trawling grounds and bays. It is commonly found in estuaries and can also venture into freshwater.