| Honorific-Prefix: | The Honourable |
| Theo Diergaardt | |
| Honorific-Suffix: | MP |
| Office: | Deputy Minister of Agriculture, Water and Forestry |
| Term Start: | 19 March 2015 |
| Term End: | 22 July 2020 |
| President: | Hage Geingob |
| Predecessor: | Lempy Lucas |
| Office2: | Deputy Minister of Lands and Resettlement |
| Term Start2: | January 2011 |
| Term End2: | 19 March 2015 |
| President2: | Hifikepunye Pohamba |
| Successor2: | Bernadus Swartbooi |
| Birth Place: | Rehoboth, Hardap Region |
| Nationality: | Namibian |
| Occupation: | Politician |
| Profession: | Accountant |
Vivian Theo Diergaardt (1969/1970 – 22 July 2020) was a Namibian politician and Member of Parliament. He was Deputy Minister of Lands and Resettlement from 2011 to 2015.
Diergaardt grew up in Rehoboth and attended school there at Dr Lemmer High School. He graduated from Peninsula Technikon with a Diploma in Cost and Management Accounting. Afterwards he obtained a Higher Diploma and a master's degree in the same discipline from Technicon SA, a distance university.[1]
Diergaardt was a SWAPO politician. He was the Regional Councillor for the Rehoboth Urban West constituency and a member of the National Council of Namibia as a representative of Hardap Region, both from 2004[1] to 2015.[2] [3] In January 2011 he was appointed Deputy Minister of Lands and Resettlement,[4] and in March 2015 he was appointed one of two Deputy Ministers of Agriculture, Water and Forestry.[5]
Diergaardt died, aged 50, after a short illness in Windhoek on 22 July 2020.[6]