A selectable one-way clutch (1) includes: a pocket plate (10); struts (12); a notch plate (20) having a plurality of notches (21); and a selector plate (30) that has a plurality of window holes (31). The strut (12) includes a protrusion (124) formed at a center thereof in a radial direction of the selectable one-way clutch (1). The selector plate (30) has a cutout groove extending from an inner surface of the window hole (31) along a formation direction of the protrusion (124). When the selectable one-way clutch (1) is disengaged, the cutout groove is fitted on the protrusion (124), and the strut (12) and the selector plate (30) overlap each other in a rotational axis direction of the selectable one-way clutch (1).