Knyaz Michael Andreas Barclay de Tolly, called by the Russians as Mikhail Bogdanovich Barklay de Tolly (Михаи́л Богда́нович Баркла́й-де-То́лли) (1761 - 1818), Russian field marshal, was born in Livonia, a descendant of a Scottish family which had settled in Russia in the 17th century. He entered the Russian army at an early age.

In 1788 - 1789 Barclay served against the Turks, in 1790 and 1794 against the Swedes and Poles. He became a colonel in 1798 and a major-general in 1799.

In the war of 1806 against Napoleon, Barclay took a distinguished part in the Battle of Pultusk (December 1806) and was wounded at the Battle of Eylau (7 February 1807), where his conduct won him promotion to the rank of lieutenant-general. In 1808 he commanded against the Swedes in Finland, and in 1809 by a rapid and daring march over the frozen Gulf of Bothnia he surprised and seized Umeå. He was made Governor-General of Finland between 1809 and 1810. In 1810 he became minister of war, and he retained that post until 1813.

During Napoleon's Invasion of Russia in 1812 Barclay was the command of the 1st Army of the West, the largest of the Russian armies facing Napoleon. Barclay proposed the now famous scorched earth tactic of drawing the enemy deep into one's own territory. Russians keenly opposed the appointment of a foreigner as commander-in-chief, and after Barclay was forced to engage Napoleon at Smolensk (17 - 18 August 1812) and defeated, the great outcry caused him to resign his command and take a subordinate place under the veteran Kutuzov.

Barclay was present at the Battle of Borodino (7 September 1812), but left the army soon afterwards. In 1813 his honor was restored by the Czar. He was re-employed in the field and took part in the campaign in Germany. After the Battle of Bautzen (21 May 1813) he once again became commander-in-chief of the Russian forces, and in this capacity he served at Dresden (26 - 27 August 1813), Kulm (29 - 30 August 1813) and Leipzig (16 - 19 October 1813). After the last battle he became a count.

Barclay took part in the invasion of France in 1814 and at Paris received the baton of a Field Marshal. In 1815 he again served as commander-in-chief of the Russian army which invaded France, and was created knyaz (prince) at the close of the war. He died at Insterburg in Prussia on 16 May (Old Style 4 May) 1818.

Barclay adopted the son of his lieutenant because he had no heir. The family name was continued as Barclay de Tolly-Weymarn .