A spinning reel includes a handle, a reel unit, a rotor, a spool, a rotor drive mechanism, and an anti-reverse mechanism. The reel unit has a fishing rod attachment portion and a mount portion. The rotor drive mechanism includes a drive gear and a pinion gear. The pinion gear is disposed in the through hole. The pinion gear is meshed with the drive gear. The anti-reverse mechanism is configured to prevent the rotor from rotating in a fishing-line releasing direction. The anti-reverse mechanism includes a one-way clutch assembly. The one-way clutch assembly is detachably attached to the mount portion of the reel unit. The rotor drive mechanism includes a seal member. The seal member is configured to seal a clearance between the pinion gear and the through hole while being disposed at a rear end of the one-way clutch assembly in the back-and forward direction.