Hesperornithoides (meaning "western bird form"; nicknamed "Lori") is a genus of troodontid theropod dinosaur that lived in North America during the Late Jurassic period.

[1] Although several Troodontid teeth were found, with the troodontid Koparion named in 1994,[2][3] a well preserved skeleton wasn't found until in 2001, a field crew from the Tate Museum supervised by William Wahl unexpectedly discovered the type skeleton Hesperornithoides in Jimbo Quarry of the Morrison Formation, overlying the excavation site of Supersaurus vivianae, near Douglas, Wyoming.

[1] The muddy sandstone layers of the Jimbo Quarry from which Hesperornithoides came from the middle Morrison Formation dating to the between the Oxfordian and Tithonian ages of the Upper Jurassic.

[1] In 2019, the type species Hesperornithoides miessleri was named and described by Scott Hartman, Mickey Mortimer, William Wahl, Dean R. Lomax, Jessica Lippincott and David M. Lovelace in an article published on PeerJ.

[7] The presence of this derived maniraptoran along with several others, such as Anchiornis and Eosinopteryx, in Jurassic sediments was a strong refutation of the temporal paradox argument used by those who oppose the consensus view that birds evolved from dinosaurs.

The exceptions all showed adaptations for an arboreal lifestyle, indicating flight developed multiple times when species evolved traits and behaviours useful for climbing trees or other more vertical surfaces, such as wing-assisted incline running.