| Honorific-Prefix: | The Honourable |
| Ruben Kun | |
| Honorific-Suffix: | MP |
| Constituency Mp4: | Buada |
| Parliament4: | Nauruan |
| Predecessor5: | Totouwa Depaune |
| Successor5: | Tamaiti Star |
| Term Start5: | 25 January 1971 |
| Term End5: | 16 November 1992 |
| Predecessor6: | Tamaiti Star |
| Successor6: | Terangi Adam |
| Term Start6: | 20 November 1995 |
| Term End6: | 8 April 2000 |
| Order3: | President of Nauru |
| Term Start3: | 19 December 1996 |
| Term End3: | 13 February 1997 |
| Deputy3: | Vinson Detenamo |
| Predecessor3: | Kennan Adeang |
| Successor3: | Kinza Clodumar |
| Office7: | Speaker of the Parliament of Nauru |
| Predecessor7: | David Peter Gadaroa |
| Successor7: | René Harris |
| Term Start7: | August 1981 |
| Term End7: | 12 December 1986 |
| Birth Name: | Ruben James Kun |
| Birth Date: | 30 March 1942[1] |
| Birth Place: | Nauru |
| Profession: | Lawyer |
Ruben James Kun (30 March 1942 - 21 September 2014)[2] was a political figure from the Pacific nation of Nauru and was president of the Republic of Nauru.
Kun was a lawyer before becoming a political figure.
He was the minister assisting the president of Nauru in the cabinets of Lagumot Harris in 1978 and 1995–1996. He was the speaker of the Parliament of Nauru from August 1981 to December 1986.[3]
He was Minister of Finance under Bernard Dowiyogo and Lagumot Harris from January 1978[4] to May 1978, and again in the cabinet of Lagumot Harris from November 1995[5] to November 1996.
Kun succeeded Kennan Adeang as president of Nauru from 19 December 1996 to 13 February 1997, and was succeeded by Kinza Clodumar.
Kun was again Minister of Finance under Bernard Dowiyogo from August 1998[6] to December 1998. Under the Pacific Solution asylum policy, Australia has an arrangement with Nauru that allows asylum seekers arriving in Australia to be detained on the island. Kun represented detainees in a case before the nation's Supreme Court.