The 1915 Birthday Honours were appointments by King George V to various orders and honours to reward and highlight good works by citizens of the British Empire. The appointments were made to celebrate the official birthday of The King, and were published in The London Gazette and in The Times on 3 June 1915.

Sir James Mackenzie was a Scottish cardiologist who was a pioneer in the study of cardiac arrhythmias. Due to his work in the cardiac field he is known as a research giant in primary care, and was knighted by King George V in 1915.