Sinomastodon ("Chinese mastodont") is an extinct gomphothere genus (of order Proboscidea) known from the Late Miocene to Early Pleistocene of Asia, including China, Japan, Thailand, Myanmar, Indonesia and probably Kashmir.

[1] Sinomastodon, in comparison to earlier gomphotheres, had a shortened (brevirostrine) lower jaw that lacked permanent tusks/incisors.

Some authors suggest that Sinomastodon originated from North American gomphotheres that migrated into Asia.

Position according to Mothé et al. 2016 supporting this hypothesis, showing Sinomastodon nested amongst North American gomphotheres:[4] †Gomphotherium †Gnathabelodon †Eubelodon †Stegomastodon †Sinomastodon †Notiomastodon †Rhynchotherium †Cuvieronius However, the teeth of the earliest Sinomastodon species from the Late Miocene are zygodont, a morphology unknown in North American gomphotheres.

[6] Specimens of Sinomastodon from the Early Pleistocene of South China (S. jiangnanensis, S. yangziensis) are suggested to have had browsing diet based on dental microwear analysis,[7] while Sinomastodon bumiajuensis from the Early Pleistocene of Java is suggested based on stable carbon isotope analysis to have been a variable feeder, with the majority of specimens found to have a predominantly grazing diet.