Brigadier General George MacLeay Macarthur-Onslow, CMG, DSO, VD (2 May 1875 – 12 September 1931) was an Australian grazier and army officer who commanded light horse units during the First World War.
When his father Arthur Onslow died in 1882, his mother Elizabeth changed her name to Macarthur-Onslow and took George and his five siblings to England in 1887.
At Katia on 5 August 1916, the 7th Light Horse, advancing in a single line, came under fire from a party of Turks some 200 metres in front of them.
Macarthur-Onslow returned to the regiment in time to take part in the Battle of Beersheba, leading the 7th on a night march around Gaza.
From May to August 1918, Macarthur-Onslow was acting commander of the 2nd Light Horse Brigade in the absence of the Brigadier General Granville Ryrie.
On 3 September 1918, he took command of the newly formed 5th Light Horse Brigade, with the temporary rank of brigadier general.