Charles William Vane (born Stewart), 3rd Marquess of Londonderry, KG, GCB, GCH (May 18, 1778) - (March 6, 1854) was a British soldier, politician and nobleman, the son (by his second wife) of Robert Stewart, 1st Marquess of Londonderry, and half-brother to Robert Stewart, Viscount Castlereagh.

Born in Dublin, Charles Stewart (as he then was) was educated at Eton, and at the age of 16 was commissioned into the British Army as a Lieutenant. He saw service in Flanders in 1794, and was Lieutenant Colonel of the 5th Dragoons by the time he helped put down the Irish Rebellion of 1798. Two years later he was elected to the Irish House of Commons as Tory representative for Thomastown, County Kilkenny, and after only two months exchanged this seat for that of County Derry, representing the same constituency at Westminster after 1801.

In 1803 Stewart was appointed aide-de-camp to George III, and four years later became Under Secretary of State for War and the Colonies. In 1809 he was made Adjutant General to Sir John Moore with the British forces fighting in the Peninsular War, a post in which he distinguished himself, particularly at the Battle of Talavera. He received the thanks of Parliament in 1810, and in 1813 was made Colonel of the 25th Light Dragoons, becoming a Knight of the Bath that same year. Until the end of the war he was Envoy Extraordinary and Minister Plenipotentiary to Berlin, and was also Military Commissioner with the allied armies, being wounded at the Battle of Kulm.

The recipient of numerous foreign honours, Stewart was also, in 1814, ennobled as Baron Stewart, of Stewart's Court and Ballylawn in the County of Donegal. That same year he received honorary degrees from Oxford and Cambridge, was admitted to the Privy Council, and was appointed a Lord of the Bedchamber to the King. He was also made Ambassador to Vienna, a post he held for nine years, and was at the Congress of Vienna with his half brother Lord Castlereagh as one of the British plenipotentiaries.

Appointed GCH in 1816, Stewart succeeded his half brother as third Marquess of Londonderry in 1822. The following year he was created Earl Vane and Viscount Seaham, of Seaham in the County of Durham, with remainder to the heirs male of the body of his second wife, Frances Anne Emily Vane-Tempest, daughter and heiress of Sir Henry Vane-Tempest, 2nd Baronet. Having married Frances in 1819, Lord Londonderry took by royal licence the surname of Vane, and used her great wealth to develop the coal fields on their Durham estates as well as to build a harbour at Seaham.

Governor of County Londonderry from 1823, Londonderry was appointed Lord Lieutenant of County Durham in 1842 and the following year became Colonel of the 2nd Life Guards. He was finally made a Knight of the Garter in 1853, and died a year later at his Park Lane home.

He was succeeded as fourth Marquess by his son from his first marriage, and as second Earl Vane by his son from his second marriage.