Who've is a contraction, a shortened form of “who have.” English speakers squeeze these two words together in casual speech and writing, dropping some letters and replacing them with an apostrophe.

You'll see who've in sentences like “Students who've finished their work can go to recess.” It works the same way as “who have” but sounds more natural and conversational.

Contractions like who've make English feel less formal and more like actual talking. You might write “who have” in a formal essay, but who've fits perfectly in a story, a friendly email, or everyday conversation. Other common contractions work the same way: “I have” becomes “I've,” “they have” becomes “they've,” and “we have” becomes “we've.”

One small warning: who've sounds almost identical to “who of,” which can create confusion when you're listening. If someone says “people who've traveled to Japan,” they mean people who have traveled there, not “people who of traveled” (which wouldn't make sense). Context usually makes the meaning clear.