The British IX Corps was an army corps formation that existed during World War I and World War II.

World War I

The IX Corps was originally formed in England in 1915 in readiness to make a new landing at Suvla during the Battle of Gallipoli. Command of the corps was given to Lieutenant General Sir Frederick Stopford based on seniority rather than competence. His handling of the corps during the August Offensive was a disaster and he was replaced only 9 days after the corps landed. His replacement in command of the corps was Lieutenant General Julian Byng.

During the Gallipoli campaign the corps comprised the following divisions:

• 10th (Irish) Division
• 11th (Northern) Division
• 53rd (Welsh) Division
• 54th (East Anglian) Division
• 2nd Mounted Division
• 29th Division - (moved from VIII Corps at Helles)

Following the British evacuation of Gallipoli, the corps was moved to France in 1916.

World War II

IX Corps saw active service in Algeria and Tunisia during WWII as part of First Army. It was disbanded after the end of the Tunisia campaign.