Hypsilurus longi, also known commonly as Long's forest dragon, is a species of lizard in the subfamily Amphibolurinae of the family Agamidae. The species is native to Papua New Guinea.
The specific name, longi, is in honor of Mark H. Long who donated to Macleay the specimen which became the holotype.
H. longi is large for its genus, and has a long tail. It may attain a snout-to-vent length (SVL) of , and a tail length three times SVL.
The preferred natural habitat of H. longi is forest, at altitudes from sea level to .
H. longi is oviparous.