| Petras Griškevičius | |
| Office: | First Secretary of the Communist Party of Lithuania |
| Term Start: | 18 February 1974 |
| Term End: | 14 November 1987 |
| Predecessor: | Antanas Sniečkus |
| Successor: | Ringaudas Songaila |
| Birth Date: | 19 July 1924 |
| Birth Place: | Kriaunos, Rokiškis District, Lithuania |
| Death Place: | Vilnius, Lithuanian SSR, Soviet Union |
| Party: | Communist Party of the Soviet Union (1945–1987) |
| Occupation: | military officer, politician |
Petras Petrovičius Griškevičius (; 19 July 1924 – 14 November 1987) was a Lithuanian communist party official in the Lithuanian SSR. He was the First Secretary of the Lithuanian Communist Party (de facto leader of Lithuania) from 1974 to his death.
He was born on 19 July 1924 in the village of Kriaunos, in the Rokiškis district of the Republic of Lithuania. He began his career in 1941 as a collective farmer in the eastern part of Chelyabinsk Region. At the beginning of World War II, Griškevičius retreated into the Russian SFSR. During the war, he was a member of the 16th Rifle Division (1942–1943) and a Soviet partisan (1943–1944) in Rokiškis district.
After joining the communist party in 1945, he slowly rose through the ranks. He worked in press censorship (1950–1955) before moving to the Vilnius City Committee of the Communist Party of Lithuania. There he worked at the secretariat (1955–1964) and central committee (1964–1971), becoming the first secretary in 1971.
After the death of Antanas Sniečkus in 1974, Griškevičius succeeded him as the First Secretary of the Lithuanian Communist Party. He was also a delegate of the Supreme Soviet of the Lithuanian SSR (since 1965), delegate of the Supreme Soviet of the Soviet Union (since 1974), and member of the Central Committee of the Communist Party of the Soviet Union (since 1976). Griškevičius was described as a Brezhnevite, conservative and "mediocre apparatchik", who opposed perestroika and especially glasnost. He supported suppression of Lithuanian history and cultural heritage, replacing them with Soviet propaganda.
He died in Vilnius on November 14, 1987, and was buried at the Antakalnis Cemetery.