This paper begins with a brief documentation of the narrowing but still persistent STEM gender gap in the United States. Arguments are then presented for the role of spatial thinking in STEM. Included are brief reviews of early work establishing spatial intelligence as a distinct human capacity and later work aimed at identifying component spatial skills. Despite continuing disagreements about how sub-skills should be categorized and labeled, there is growing consensus that spatial thinking is entailed in STEM disciplines, and that individuals with better spatial skills are more likely to enter, remain, and excel in STEM. Also reviewed are data showing male advantages on spatial skills. Combining the need for spatial thinking in STEM with gender differences in spatial skills generates the suggestion that spatial interventions may help reduce the STEM gender gap. Arguments and empirical findings from spatial intervention studies are then reviewed. Extant work permits the conclusion that spatial interventions can advance performance on spatial tasks, but is not yet conclusive about their impact on STEM outcomes in general or on the STEM gender gap in particular. The paper ends by highlighting some remaining questions and recommending approaches for future research.