A key debate in the psychology of ideology is whether leftists and rightists are psychologically similar or different. A long-standing view holds that left-wing and right-wing people are meaningfully different from one another across a whole host of basic personality and cognitive features. Scholars have recently pushed back, suggesting that left-wing and right-wing people are more psychologically similar than distinct. We review evidence regarding the psychological profiles of left-wing and right-wing people across a wide variety of domains, including their dispositions (values, personality, cognitive rigidity, threat-sensitivity, and authoritarianism), information processing (motivated reasoning and susceptibility to misinformation), and their interpersonal perceptions and behaviors (empathy, prejudice, stereotyping, and violence). Our review paints a nuanced picture: People across the ideological divide are much more similar than scholars sometimes appreciate. And yet, they differ—to varying degrees—in their personality, values, and (perhaps most importantly) in the groups and causes they prioritize, with important implications for downstream attitudes and behavior in the world.