Shirleya grahamae Pigg & DeVore gen. et sp. nov. (Lythraceae) is established for silicified fruits from the middle Miocene Yakima Canyon of central Washington State, USA. The capsules are 10 mm long × 11.5-12.5 mm wide, enclosed in a persistent floral tube and contain 5-7 locules. They are loculicidally dehiscent, fracturing into fragments and leaving the central axis free. Placentation is axile. Five to seven mature seeds are tightly packed per locule, often with several smaller seeds. Seeds are winged, anatropous, and narrowly attached subapically to the central axis, curving basally and radially within the fruit. They are up to ∼4.6 mm long × 1.9 mm wide, with a small, triangular embryo cavity and a prominent distal wing. The inflated wing is filled with a bilobed parenchymatous pad of tissue with a central cavity. Shirleya grahamae is assigned to the Lythraceae, and is most similar to Lagerstroemia, based on the synapomorphies of distally winged seeds and revolute cotyledons. Shirleya differs from Lagerstroemia in seed arrangement, and pericarp and wing anatomy. This study provides the first anatomical information about a Miocene Lagerstroemia-like fruit and documents further diversity of the Lythraceae in the Neogene of northwestern North America.