| Sir John Jensen | |
| Office1: | Secretary of the Department of Munitions |
| Term Start1: | 1 January 1942 |
| Term End1: | 5 April 1948 |
| Office2: | Secretary of the Department of Supply and Development |
| Term Start2: | 6 July 1948 |
| Term End2: | 31 July 1949 |
| Birth Name: | John Klunder |
| Birth Date: | 20 March 1884 |
| Birth Place: | Bendigo, Victoria |
| Death Place: | Hawthorn, Melbourne, Victoria |
| Resting Place: | Box Hill Cemetery |
| Occupation: | Public servant |
| Nationality: |  Australian |
| Spouse: | Maria Ruby Gordon (m. 1911) |
Sir John Klunder Jensen (20 March 188417 February 1970) was a senior Australian public servant. He was Secretary of the Department of Munitions between 1942 and 1948.
John Jensen was born in Bendigo, Victoria on 20 March 1884.
He joined the Commonwealth Public Service in 1901, the year of Australia's federation and the year the service was first established.
In 1920, Jensen visited the United States on rifle-manufacturing business, and he went on to study factory administration in England and in the United States.[1]
In January 1942, Jensen was appointed Secretary of the Department of Munitions.[2] During his time as permanent head of the Munitions department, he was a member of the Allied Supply Standing Committee and the executive of the Allied Supply Council. In the role, he played a leading part in organizing munitions supply during World War II.[3] His department was abolished in 1948 after scaling down after the world war. At this time, Jensen was moved to head the Department of Supply and Development. In his role at the Department of Supply and Development, he found himself frequently journeying to South Australia, including to visit the Woomera Rocket Range, and in connection to uranium mining.[4]
Jensen retired in 1949. Immediately after retirement he took work as a member of the Commonwealth Immigration Planning Council.
On 17 February 1970, Jensen died in Hawthorn, Melbourne.
In 1938, Jensen was appointed an Officer of the Order of the British Empire. In the 1950 Birthday Honours he was made a Knight Bachelor, for services to munitions production.
In December 1969, the Victorian headquarters of the Department of Supply was named Jensen House in John Jensen's honour.