Walter Leslie (Fetternaer House, Aberdeenshire, 1607 – Vienna, March 4, 1667) was an Imperial Field Marshal of Scottish descent.
Walter Leslie was born in a prominent Scottish noble family from the Clan Leslie. His father William was the 10th Baron of Balquhain and his mother Joan was a daughter of John Baron of Gogar. In 1647, he married Anna Francesca von Dietrichstein, daughter of Count Maximilian von Dietrichstein. They had no children.
Walter Leslie entered in 1631 in the service of Albrecht von Wallenstein and fought together with his countryman John Gordon in the Battle of Lützen. Leslie was responsible for the supply of ammunition to Wallenstein's army and had thus good contacts with the court in Vienna. There he was ordered to keep an eye on Wallenstein, whose loyalty was mistrusted in Vienna. When Wallenstein had to flee in 1634 to Eger, Lesley witnessed Wallenstein's plans to link up with the enemy.
Then Leslie supposedly plotted with John Gordon and Irishman Walter Butler to kill the traitor Wallenstein. On February 25 a fight broke out during a banquet in the house of the mayor of Eger in which Wallenstein, Trčka, Ilow and Wilhelm Kinsky were killed and Leslie wounded.
Already in April 1634 Emperor Ferdinand II rewarded Leslie for his action by making him Colonel of a regiment. Later he received the rule of Neustadt an der Mettau and he converted to Catholism.
In summer 1634 Leslie participated in the Siege of Regensburg and on September 5, 1634 in the Battle of Nördlingen. Since 1636 he pursued a military-diplomatic career and became in 1646 Feldzeugmeister. In 1650 he became Field Marshal, Vice-President of the Hofkriegsrat and in 1665 Knight in the Order of the Golden Fleece.