Abstract: A lawn mower barrier (3; 3?) for restricting autonomous lawn mowers (2) to a designated area (4). The lawn mower barrier comprises an elongate, pliable barrier body (5; 5?) with two terminal ends (6a,b; 6a?,b?), the barrier body (5; 5?) is a fluid proof container comprising a hollow space (7); the terminal ends (6a,b; 6a?,b?) are configured for connection to each other to form a closed loop, and the lawn mower barrier (3; 3?) comprises a valve (12a; 12b) for filling the barrier body (5) with a fluid.