Humpback whales (Megaptera novaeangliae) are a species whose social behavior has been studied for decades, but whose sexual behavior remains largely undescribed. Most humpback whales spend the summer months feeding in polar waters and migrate during fall and winter months to tropical waters, where the observed behaviors are related largely to reproduction (Chittleborough, 1965; Craig et al., 2003; Currie et al., 2018). Despite decades of research on humpback whales around the world, reports of penis extrusion by males are relatively rare (Herman et al., 2007; Pack et al., 1998, 2002) and copulation in humpback whales has not yet been documented (Ransome et al., 2021). This is the first report of penetration by a humpback whale, and the first report of sexual activity between two male humpback whales. ; Full Text