Byron Plantagenet Cary, 12th Viscount Falkland (3 April 1845 – 10 January 1922) was a Scottish peer and British Army officer.

Cary was the eldest son of Capt. Byron Cary, the third son of Capt. Charles Cary, 9th Viscount Falkland.^[1]

Cary was educated at the Royal Military College, Sandhurst, and on 4 August 1863, purchased an ensigncy in the 49th Regiment of Foot.^[2] He was promoted lieutenant on 9 August 1867,^[3] and exchanged into the 35th Regiment of Foot on 23 October.^[4] He was subsequently promoted captain on 24 November 1877,^[5]

Cary married Mary, daughter of Robert Reade, Esq., of New York, on 25 September 1879. They had three sons and three daughters:

• Lucius Cary, 13th Viscount Falkland (1880–1961)
• Hon. Catherine Mary Cary (29 May 1882 – 16 October 1972), married Godfrey Dalrymple-White in 1912
• Hon. Mary Selina Cary (10 November 1884 – 6 November 1960)
• Lt-Cdr The Hon. Byron Plantagenet Cary, DSO (25 January 1887 – 16 September 1917), lost commanding HMS G9
• Hon. Lettice Cary (29 September 1888 – 19 December 1963), married in 1918 Commander Ralph Neville (1887–1936) and in 1937 Major Philip Pearson-Gregory
• Hon. Philip Plantagenet Cary (1895–1968)

Cary was seconded for staff service on 10 April 1880.^[6] He was subsequently promoted to major in his regiment, which became the Royal Sussex Regiment during the Childers Reforms of 1881, and served as aide-de-camp to Major-General Percy Feilding in Malta. Cary retired on 5 March 1884 with the honorary rank of lieutenant-colonel.^[7] In 1886, he succeeded his uncle, Admiral Plantagenet Cary, 11th Viscount Falkland, in the peerage.^[1]

In April 1893, he was appointed a deputy lieutenant of the North Riding of Yorkshire,^[8] and was given the honorary rank of colonel in the 4th (Militia) Battalion of the Green Howards, of which he was lieutenant-colonel.^[9] Falkland was elected a representative peer for Scotland in 1894, and sat in the House of Lords until his death. He retired from the Army on 11 November 1896.^[10] Falkland died in 1922, and was succeeded by his eldest son Lucius Cary, 13th Viscount Falkland.