Acostasaurus (meaning "Acosta's lizard") is an extinct genus of possibly Thalassophonean pliosaurid known from the Barremian of the Paja Formation, Colombia.

The sclerotic ring of the specimen is also very large, suggesting that Acostasaurus was adapted to see in deep or murky waters.

The short, wide symphysis is one of the features which differentiates Acostasaurus from other contemporary pliosaurids such as the various brachauchenine pliosaurs from the formation.

[1] Other pliosaurids which possess this condition include the Jurassic taxon Simolestes, which like Acostasaururs has large orbits, as well as a short symphysis.

As discussed before, Simolestes and other less derived pliosaurids possess similar dentition, especially in the arrangement that are present in Acostasaurus.