Ulmus okanaganensis is an extinct species of flowering plant in the family Ulmaceae related to the modern elms.

The type description listed occurrences at the 49 million year old Klondike Mountain Formation near Republic, Washington plus the British Columbian sites of One Mile Creek near Princeton, British Columbia, the McAbee Fossil Beds east of Cache Creek, and in the Driftwood Canyon Provincial Park northeast of Smithers.

[4] Ulmaceous fruits from the Princeton area had been tentatively identified as a species of Chaetoptelea,[5] a southern North American genus that is now included into Ulmus.

Fossils of leaves and fruits that had previously been identified as Zelkova and Chaetoptelea along with additional specimens were studied by paleobotanists Thomas Denk and Richard Dillhoff, with the type description for U. okanaganensis being published in a 2005 Canadian Journal of Botany article.

[1] They chose the specific name okanaganensis, in reference to the Okanagan Highlands, of Central British Columbia and northern Washington, where the species is a common paleofloral element of the Eocene lake deposits in the region.

[1] The species Early Eocene Ulmus fushunensis described in 2010 from the Jijuntun Formation of Liaoning Province, China, displays noted similarities to U. okanaganensis as well.

The primary vein ranges between fully straight and slightly curved as it progresses from base to tip.