| Conflict: | Convoy HG 84 |
| Partof: | World War II |
| Date: | 14–17 June 1942 |
| Place: | eastern Atlantic |
| Result: | Inconclusive |
| Combatant1: | Germany |
| Combatant2: | United Kingdom |
| Commander1: | Karl Dönitz |
| Commander2: | Hubert Hudson Frederic Walker |
| Strength1: | 9 U-boats |
| Strength2: | 23 Ships 7 Escorts |
| Casualties1: | 3 U-boats damaged |
| Casualties2: | 5 Ships sunk |
HG 84 was an Allied convoy of the HG (Homeward from Gibraltar) series during World War II.
Following the U-boat Arm's defeat whilst attacking convoy HG 76, the U-boat high command, Befehlshaber der U-Boote (BdU), had temporarily stopped attacks against convoys on the Gibraltar route. This was overtaken by the shift in focus to Operation Drumbeat, the offensive against US shipping off the American east coast, and for six months the route was left undisturbed. Seven outbound and seven homebound convoys, averaging 20 ships each, sailed without loss over a six-month period. In June 1942 BdU determined that renewing the attack there would be profitable once more as it would achieve strategic surprise.
HG 84 comprised 20 ships homeward bound from Gibraltar, many in ballast, or carrying trade goods.The convoy commodore was Captain Hubert Hudson, who had been the navigator on the Imperial Trans-Antarctic Expedition, in Pelayo, and the convoy was protected by an understrength escort group. This was 36th Escort Group, consisting of the sloop and three corvettes, and, under the command of F.J. Walker. The convoy was accompanied by a CAM ship,, and the rescue ship Copeland.
Ranged against them was the wolfpack Endrass (named for the U-boat commander Engelbert Endrass) of nine U-boats (U-71, U-84, U-89, U-132, U-134, U-437, U-552, U-571, U-575).
Convoy HG 84 sailed from Gibraltar on 9 June 1942, undetected by Axis patrols. On 11 June the convoy was joined by three ships bound from Lisbon to the UK. However these ships had been shadowed by German aircraft, Fw 200 Condors based at Bordeaux, and these maintained contact while the Endrass boats moved to intercept. On 14 June U-552 (German: [[Kapitänleutnant]] Erich Topp) made contact with the convoy, to be joined that evening by three others, U-89, U-132 and U-437. The escorts were able to pinpoint the shadowing U-boats by HF/DF and conducted an aggressive defence, attacking the U-boats as they attempted to close.
Stork and Gardenia attacked U-132, causing severe damage and forcing her to abandon the battle and leave the pack. Marigold and Convolvulus attacked U-89 and U-437 over a period of 31 hours. U-552 was able to penetrate the screen and made two attacks. The first, just after midnight on 14/15 June, hit and sank the ships Etrib, Pelayo and Slemdal. The Convoy Commodore, Hudson, on Pelayo, was among those lost. Four hours later, having reloaded, U-552 again penetrated the escort screen and sank two more ships, and . During the next day, 15 June, five more boats arrived, but Walker's ships continued their aggressive defence, fiercely attacking all attempts by the U-boats to close on the convoy. During this period U-552 and U-71 both suffered damage and had to withdraw. U-575 managed to close and fire but her torpedoes missed and there was no damage.
On 16 June the convoy was joined by three more warships, the destroyer and frigates and . The convoy also came within range of Coastal Command aircraft, and these were able to further suppress any U-boat attacks. The convoy was also in range of German aircraft, and during the day the convoy was attacked by Junkers Ju 88 dive-bombers. Wild Swan came under attack while investigating a group of Spanish trawlers which came close to the convoy. She, and the trawlers, were bombed and Wild Swan, with four of the Spanish trawlers, were sunk. On 17 June, with the arrival of yet more Allied aircraft, BdU called off the attack. Convoy HG 84 arrived at Liverpool on 20 June without further loss.
Whilst the U-boat Arm had had some success, it was not the victory BdU had expected. Three of the nine U-boats had been severely damaged, though only two, U-71 and U-552 had to return to base; U-132 was able to carry out repairs at sea and was able to continue her patrol. HG 84 had lost five ships, yet 17 ships arrived safely. Walker was commended for his handling of the defence, and it was recognized he had been able to prevent further losses despite the disparity in numbers and to avert a big defeat.
| 15 June 1942 | Etrib | British | 4 | U-552 | |
| 15 June 1942 | Pelayo | British | 17 | 1,345 GRT | U-552 |
| 15 June 1942 | Slemdal | Norwegian | nil | 7,374 GRT | U-552 |
| 15 June 1942 | British | 1 | 2,759 GRT | U-552 | |
| 15 June 1942 | British | 13 | 2,436 GRT | U-552 | |