| Honorific-Prefix: | Samdech |
| Penn Nouth | |
| Native Name: | Central Khmer: ប៉ែន នុត |
| Office: | Prime Minister of Cambodia |
| Term Start: | 17 April 1975 |
| Term End: | 4 April 1976 |
| Successor: | Khieu Samphan (acting) |
| Term Start2: | 31 January 1968 |
| Term End2: | 14 August 1969 |
| President2: | Norodom Sihanouk |
| Predecessor2: | Son Sann |
| Successor2: | Lon Nol |
| Term Start3: | 28 January 1961 |
| Term End3: | 17 November 1961 |
| Predecessor3: | Pho Proeung |
| Successor3: | Norodom Sihanouk |
| President3: | Norodom Sihanouk |
| Term Start4: | 17 January 1958 |
| Term End4: | 24 April 1958 |
| Predecessor4: | Ek Yi Oun |
| Successor4: | Sim Var |
| Term Start5: | 18 April 1954 |
| Term End5: | 26 January 1955 |
| Monarch5: | Norodom Sihanouk |
| Predecessor5: | Norodom Sihanouk |
| Successor5: | Leng Ngeth |
| Term Start6: | 24 January 1953 |
| Term End6: | 22 November 1953 |
| Monarch6: | Norodom Sihanouk |
| Predecessor6: | Norodom Sihanouk |
| Successor6: | Chan Nak |
| Term Start7: | 15 August 1948 |
| Term End7: | 21 January 1949 |
| Monarch7: | Norodom Sihanouk |
| Predecessor7: | Chhean Vam |
| Successor7: | Yem Sambaur |
| Office8: | Minister of Foreign Affairs |
| Primeminister8: | Ek Yi Oun Sim Var |
| Term Start8: | 11 January 1958 |
| Term End8: | 10 July 1958 |
| Predecessor8: | Sim Var |
| Successor8: | Truong Cang |
| Birth Date: | 15 April 1906 |
| Birth Place: | Phnom Penh, Cambodia, French Indochina |
Penn Nouth (Central Khmer: ប៉ែន នុត; 15 April 1906 – 18 May 1985) was a Cambodian politician. He served in the French colonial administration, then took active part in Cambodian politics, was several times Prime Minister of Cambodia (1953, 1954 - 1955, 1958, 1961) as part of the Sangkum regime of Prince Norodom Sihanouk. He was the first prime minister of an independent Cambodia. He was prime minister for the sixth time from 31 January 1968 to 14 August 1969. On 18 March 1970, when Norodom Sihanouk was deposed by Penn Nouth's successor Lon Nol, Penn Nouth joined the monarch in his exile and became prime minister in the GRUNK coalition. His combined tenure as Prime Minister (5 years, 222 days), spanning seven non-consecutive terms, is the second-longest in Cambodian history after Hun Sen.
After the Khmer Rouge took Phnom Penh in 1975, he served as prime minister of the country for the last time, but did not have real power. He was allowed to leave Cambodia in 1979 along with Sihanouk; he then emigrated.