An electronic device may be provided with antennas. Antennas for the electronic device may be formed from slot antenna structures. A slot antenna structure may be formed from portions of a metal housing for an electronic device. The slots of the slot antenna structures may be indirectly fed to form first and second indirectly fed slot antennas. The first and second indirectly fed slot antennas may be formed from slots in a rear surface of an electronic device and a sidewall of the electronic device. The slots may have open ends along an edge of the sidewall and may have closed ends that face each other. A hybrid antenna may also be formed in the electronic device.