The Battle of Lone Pine, also known as the Battle of Bloody Ridge (Turkish: Kanlı Sırt Muharebesi), was fought between Australian and New Zealand Army Corps (ANZAC) and Ottoman Empire forces during the Gallipoli campaign of the First World War, between 6 and 10 August 1915. The battle was part of a diversionary attack to draw Ottoman attention away from the main assaults being conducted by British, Indian and New Zealand troops around Sari Bair, Chunuk Bair and Hill 971, which became known as the August Offensive.

At Lone Pine, the assaulting force, initially consisting of the Australian 1st Brigade, managed to capture the main trench line from the two Ottoman battalions that were defending the position in the first few hours of the fighting on 6 August. Over the next three days, the fighting continued as the Ottomans brought up reinforcements and launched numerous counterattacks in an attempt to recapture the ground they had lost. As the counterattacks intensified the ANZACs brought up two fresh battalions to reinforce their newly gained line. Finally, on 9 August the Ottomans called off any further attempts and by 10 August offensive action ceased, leaving the Allies in control of the position. Nevertheless, despite the ANZAC victory, the wider August Offensive of which the attack had been a part failed and a situation of stalemate developed around Lone Pine which lasted until the end of the campaign in December 1915 when Allied troops were evacuated from the peninsula.

The Lone Pine battlefield was named for a solitary Turkish pine that stood there at the start of the fighting; The tree was also known by the Anzac soldiers as the "Lonesome Pine". The battlefield was situated near the centre of the eastern line of the Australian and New Zealand trenches around Anzac Cove on a rise known as "400 Plateau" that joined "Bolton's Ridge" to the south with the ridge along the east side of "Monash Valley" to the north. Being towards the southern end of the area around Anzac Cove, the terrain in the Lone Pine region was comparatively gentle and the opposing trenches were separated some distance with a flat no-man's land intervening. Due to its location relative to the beachhead and the shape of the intervening ground, Lone Pine's importance lay in the fact that its position provided a commanding view of the Australian and New Zealand rear areas. From the 400 Plateau it was possible to observe as far south as Gaba Tepe and its possession would have afforded the Ottomans the ability to place the approaches to the Second Ridge under fire, preventing the flow of reinforcements and supplies from the beachhead to the forward trenches.

The main part of the Australian position at Lone Pine was centred on a feature known as "The Pimple", where a salient had developed at the point where the Australians' position was closest to the Ottoman line. To the east of the salient, opposite The Pimple, the Ottoman line extended from the head of a gully—known as "Owen's Gulley" by the Australians—south for 400 yards (370 m) towards the neck of Bolton's Ridge and continued south along a spur called "Sniper's Ridge". Because of the salient around The Pimple, the Ottomans had focused on developing the trenches along the flanks of the position more than the centre, and had placed the firing positions in the centre in depth in order to gain the advantage of being able to pour enfilade fire upon any attacking force. At the rear of the Ottoman line, near Owen's Gully, was a depression called "The Cup" that was not visible from the Australians' position on The Pimple. Despite overflights of the area by British reconnaissance aircraft in June, the Australians were unaware of The Cup's existence, and at the time of the attack they believed this area to be flat and to consist of further trench lines. In reality it was actually a reserve area where the Ottomans had established a regimental headquarters and sited a series of bivouacs in terraces and at the time of the attack there were large numbers of reinforcements camped there.

Prior to the battle, isolated fighting around Lone Pine had begun early in the Gallipoli campaign. At around 7:00 a.m. on the first day of the Australian and New Zealand landings at Anzac Cove, 25 April 1915, elements of the Australian force had pushed through to Lone Pine in an effort to destroy an Ottoman artillery battery that had been firing down upon the landing beach. Before the Australians could engage the battery, the Ottomans had withdrawn to a ridge to the south-west, which the Australians later dubbed "Third Ridge" (or "Gun Ridge"). Pressing further inland, troops from the 6th Battalion had attempted to reach the ridge, crossing a wide valley (later known as "Legge Valley"), but they were pushed back when an Ottoman regiment, the 27th, had launched a counterattack from the south-east towards Lone Pine at 10:00 a.m., with the objective of retaking the 400 Plateau. Rolling up the 6th Battalion, the Ottomans pushed the Australians back to Pine Ridge, a finger of land that jutted south from Lone Pine towards Gaba Tebe. Taking heavy casualties, the Australians withdrew north to Lone Pine, where they were able to establish a defensive position. As reinforcements were brought up from New Zealand units, in the afternoon a second Ottoman regiment, the 77th, arrived and heavy hand-to-hand fighting ensued before the counterattack was blunted. Further fighting around Lone Pine continued throughout the early stages of the campaign, but eventually a stalemate developed in which neither side was able to advance and static trench warfare began.

In early July 1915, while making plans for an offensive to break the deadlock that had developed around the Gallipoli Peninsula following the initial landings in April, the commander of the Australian and New Zealand Army Corps, Lieutenant General William Birdwood, had determined that an attack at Lone Pine could be used to divert Ottoman attention away from a main attack that would be launched by a combined force of British, Indian and New Zealand troops further north around Sari Bair, Chunuk Bair and Hill 971. The Australian 1st Infantry Brigade was chosen to undertake the attack on Lone Pine, and consisted of about 3,000 men, under the command of a British officer, Colonel Nevill Smyth. Along with the 2nd and 3rd Infantry Brigades, the 1st Infantry Brigade was part of the Australian 1st Division. The division's commander was Brigadier General Harold Walker, a British officer who had replaced Major General William Bridges as temporary commander after Bridges had been killed by a sniper in May. Walker did not like the idea of launching an attack at Lone Pine, let alone a mere diversion, but when General Sir Ian Hamilton, the commander of the Mediterranean Expeditionary Force, insisted the attack proceed, through thorough planning, Walker endeavoured to give his troops the best chance of success possible on such an unfavourable battleground.

The Ottoman forces opposing the Australians at Lone Pine consisted of two battalions from the 47th Regiment, under the command of Tevfik Bey. These battalions amounted to a total of about 1,000 men, of which 500 were positioned in the trenches along the front, while another 500 were positioned further back in depth. Sitting further back in divisional reserve, to the north-east on "Mortar Ridge", was a battalion from the 57th Regiment, which had been relieved from its position on the front line north of Lone Pine by an Arab battalion of the 72nd Regiment. The positions north and south of the Ottoman line at Lone Pine were held by the 125th Regiment at Johnston's Jolly in the north and the 48th Regiment in the south along Pine Ridge.

The width of the front of the attack was 160 yards (150 m) and the distance between the two trench lines was about 60–100 yards (55–91 m). To reduce the distance to be crossed, the Australians projected a number of tunnels towards the Ottoman trenches from The Pimple. Immediately after the attack, one of these tunnels was to be opened along its length to make a communications trench through which reinforcements could advance without having to cross the exposed ground. Some of the attackers would have to make the advance over open ground from the Australian trench line. To provide some measure of protection for these men, three mines were set by engineers to make craters in which they could seek shelter. The preliminary bombardment was stretched over three days—initially confined to a limited "slow shoot", building up to a final intense bombardment an hour before the assault—and was successful in cutting much of the barbed wire that the Ottomans had placed in front of their position. The preparation stage of the attack began at 2:00 p.m. on 6 August, when the Australians detonated the three mines they had dug in front of the Ottoman lines, in an attempt to create cover for the advancing troops. Two and a half hours later the final heavy preliminary bombardment commenced, with Australian, British and New Zealand artillery batteries firing on the Ottoman trench line, while naval gunfire support from the British cruiser HMS Bacchante provided counter-battery fire on Ottoman artillery positioned along Third Ridge. Retreating into tunnels which had been cut as part of mining operations, the majority of the forward Ottoman troops were able to find shelter from the bombardment that lasted for an hour.