Fastnet

Fastnet can refer to:
 * Fastnet International Schools Regatta, a regatta held in County Cork, Ireland
 * Fastnet Line, a passenger ferry service operating between Wales and Ireland
 * Fastnet (netball), a variation of the rules of netball used primarily in the World Netball Series
 * Fastnet Race, one of the four or so most prestigious ocean races in competitive sailing
 * Fastnet Rock, a small clay-slate island with quartz veins and the most southerly point of Ireland
 * A sea area, named for the rock, used in the British Shipping Forecast
 * Fastnet Rock (horse), an Australian thoroughbred racehorse stallion
 * FastNet, the business name of South African communication service provider Swiftnet Pty Ltd, a subsidiary of Telkom