Operation Pluto (Pipeline Under the Ocean or Pipeline Underwater Transportation of Oil, also written Operation PLUTO) was an operation by British engineers, oil companies and the British Armed Forces to construct submarine oil pipelines under the English Channel in support of Operation Overlord, the Allied invasion of Normandy during the Second World War.

The British War Office estimated that petrol, oil and lubricants would account for more than 60 per cent of the weight of supplies required by the expeditionary forces. Pipelines would reduce the reliance on coastal tankers, which could be affected by bad weather, were subject to air attack, and needed to be offloaded into vulnerable storage tanks ashore. A new kind of pipeline was required which could be rapidly deployed, and two types were developed, named "Hais" and "Hamel" after their inventors.

Camouflaged pumping stations were established at Sandown on the Isle of Wight, and at Dungeness on the Kent coast, which were connected to the Avonmouth-Thames pipeline. Two pipeline systems were laid: one, codenamed "Bambi", from Sandown to Cherbourg and the other, "Dumbo", from Dungeness to Boulogne.

Deployment of Bambi commenced on 12 August 1944. It was not very successful, delivering only 3,300 long tons (3,400 t) between 22 September, when the first pipeline became operational, and 4 October, when the Bambi project was terminated.

The Dumbo system was more successful. The first pipeline commenced pumping on 26 October, and remained in action until the end of the war. By December, a total of 17 pipelines had been laid. The Dumbo system was shut down on 7 August 1945, by which time the pipelines had carried 180 million imperial gallons (820 million litres) of petrol.

The Pluto pipelines were responsible for about 8 per cent of the deliveries of petroleum products from the United Kingdom to the Allied Expeditionary Force in North West Europe.