Bardia, or El Burdi (Arabic: البردية or البردي‎) is a Mediterranean seaport in the Butnan District of eastern Libya. It is also known as Bórdi Slemán.

In Roman times the town was known as Petras Maior.

During World War I, German U-boats made several landings in the port of Bardia in support of the Senussi order during their revolt against British and Italian colonial rule.

During World War II, it was the site of a major Italian fortification, invested by the XXIII Corps under the command of General Annibale Bergonzoli. On 21 June 1940, the town was bombarded by the 7th Cruiser Squadron of the Mediterranean Fleet. In this fleet was the cruiser HMAS Sydney. The town was taken during Operation Compass by Commonwealth forces consisting mainly of the Australian 6th Division in fighting over 3–5 January 1941.

The Axis later reoccupied the town and set up a prisoner of war camp there. On 2 January 1942, Bardia was re-taken by the South African 2nd Infantry Division, including New Zealand cavalry units. The South Africans, many of them ill-trained and ill-equipped police, lost hundreds of men, but the operation freed some 8,000 Allied prisoners of war and took some 6,000 Axis prisoners.

The Battle of Bardia was fought over three days between 3 and 5 January 1941, as part of Operation Compass, the first military operation of the Western Desert Campaign of the Second World War. It was the first battle of the war in which an Australian Army formation took part, the first to be commanded by an Australian general and the first to be planned by an Australian staff. Major General Iven Mackay's 6th Division assaulted the strongly held Italian fortress of Bardia, Libya, assisted by air support and naval gunfire, and under the cover of an artillery barrage. The 16th Infantry Brigade attacked at dawn from the west, where the defences were known to be weak. Sappers blew gaps in the barbed wire with Bangalore torpedoes and filled in and broke down the sides of the anti-tank ditch with picks and shovels. This allowed the infantry and 23 Matilda II tanks of the 7th Royal Tank Regiment to enter the fortress and capture all their objectives, along with 8,000 prisoners.

In the second phase of the operation, the 17th Infantry Brigade exploited the breach made in the perimeter, and pressed south as far as a secondary line of defences known as the Switch Line. On the second day, the 16th Infantry Brigade captured the township of Bardia, cutting the fortress in two. Thousands of prisoners were taken, and the Italian garrison now held out only in the northern and southernmost parts of the fortress. On the third day, the 19th Infantry Brigade advanced south from Bardia, supported by artillery and the Matilda tanks, now reduced in number to just six. Its advance allowed the 17th Infantry Brigade to make progress as well, and the two brigades reduced the southern sector of the fortress. Meanwhile, the Italian garrisons in the north surrendered to the 16th Infantry Brigade and the Support Group of the British 7th Armoured Division outside the fortress. In all, some 36,000 Italian prisoners were taken.