A ‘T’-antenna, ‘T’-aerial, or flat-top antenna is a monopole radio antenna consisting of one or more horizontal wires suspended between two supporting radio masts or buildings and insulated from them at the ends. A vertical wire is connected to the center of the horizontal wires and hangs down close to the ground, connected to the transmitter or receiver. Combined, the top and vertical sections form a ‘T’ shape, hence the name. The transmitter power is applied, or the receiver is connected, between the bottom of the vertical wire and a ground connection. ‘T’-antennas are typically used in the VLF, LF, MF, and shortwave bands,^{: 578–579} and are widely used as transmitting antennas for amateur radio stations, and long wave and medium wave AM broadcasting stations. They can also be used as receiving antennas for shortwave listening.

The ‘T’-antenna functions as a monopole antenna with capacitive top-loading; other antennas in this category include the inverted-‘L’, umbrella, and triatic antennas. It was invented during the first decades of radio, in the wireless telegraphy era, before 1920.