Abstract: An electronic device may have first and second rear-facing displays, a front-facing display, a cover at a front side overlapping the front-facing display, and an antenna that radiates through the cover. The cover may have a three-dimensional curvature. The device may have an inner chassis and an outer chassis. The antenna may include a radiating element and a ground trace on a flexible printed circuit. To maximize wireless performance of the antenna, the ground trace may be electrically coupled to as much conductive material in the vicinity of the antenna as possible. For example, the ground trace may be grounded to conductive structures in the front-facing display via a conductive cavity for the antenna, may be grounded directly to the outer chassis using conductive screws, and/or may be grounded directly to the inner chassis using conductive screws.