Count Peter Alekseyevich Pahlen (Russian: Пётр Алексе́евич Па́лен; German: Peter Ludwig von der Pahlen; 28 July 1745 – 25 February 1826) was a Russian courtier who played a pivotal role in the assassination of Emperor Paul. He became a general in 1798, a count in 1799, and was the Military Governor of St. Petersburg from 1798 to 1801.
Pahlen stemmed from a family of Baltic nobles. He was born in the manor of Palmse, in present-day Vihula Parish, Lääne-Viru County, Estonia. He served in the horse guards and saw service in the Russo-Turkish Wars. He was wounded at Bendery and invested with the Order of St George of the 4th degree. During the Russo-Turkish War, 1787-92 he distinguished himself during the Siege of Ochakov (order of St. George the 3rd degree).
In 1787 Pahlen was put in charge of the Riga Governorate. He conducted the negotiations leading to the incorporation of Courland, Semigalia, and other Biron possessions into the Russian Empire. After that, he was appointed the first Governor General of Courland guberniya (1795).
On December 3, 1796 Pahlen was appointed to command the Cuirassier Regiment of Riga, but soon the new Emperor made him regret his former contacts with the disgraced prince Platon Zubov. In January 1797 Pahlen was discharged from the governorship, and on 26 February he was relieved from his post in the regiment and excluded from the service.