RAF Hell's Mouth was a World War II Royal Air Force grass airfield at Hell's Mouth, (Porth Neigwl) on the Llŷn Peninsula near Abersoch, Gwynedd.
RAF Hell's Mouth was commissioned in February 1937 as a Relief Landing Ground, later an Emergency landing Ground for RAF Penrhos. It was also an air gunnery and bombing range, with targets on the land, floated 1 mile offshore and towed drogues in the air. A small range railway was in use to provide moving targets. The site was decommissioned in 1945 and returned to agriculture.
Typical aircraft using the airfield were Bristol Blenheim and Armstrong Whitworth Whitley. In August 1944 a Vickers Wellington was successfully landed by a Polish pilot followinmg an engine failure. Despite the mismatch in size, the aircraft also was able to subsequently take off.