The Battle of Thiepval Ridge was the first large offensive of the Reserve Army, during the Battle of the Somme on the Western Front during the First World War. The attack was intended to benefit from the Fourth Army attack in the Battle of Morval, by starting 24 hours afterwards. The battle was fought on a front from Courcelette in the east, near the Albert–Bapaume road, to Thiepval and the Schwaben Redoubt in the west, which overlooked the German defences further north in the Ancre valley, the rising ground towards Beaumont-Hamel and Serre beyond.

The Reserve Army was a field army of the British Army and part of the British Expeditionary Force during the First World War. On 1 April 1916, Lieutenant-General Sir Hubert Gough was moved from the command of I Corps and took over the Reserve Corps, which in June before the Battle of the Somme, was expanded and renamed Reserve Army. The army fought on the northern flank of the Fourth Army during the battle and became the Fifth Army on 30 October.