| Reserve Officer School | |
|---|---|
&sq=Qlik&lang=&file=File:RUK-lippu.jpg) The Colour of the School | |
| Active | 1920–1942: Reserviupseerikoulu 1942–1945: Upseerikoulu 1948– Reserviupseerikoulu |
| Country |  Finland |
| Branch | &sq=Qlik&lang=&file=File:Suomen_Maavoimien_tunnus.svg){kind=small} Finnish Army |
| Type | Military school |
| Role | Reserve officer training |
| Size | 200 conscripts, 250 career personnel, 700 students during courses[1] |
| Part of | Army Academy |
| Garrison | Hamina |
| Nickname(s) | Rukki, Ruk |
| March | Heroes pugnate |
| Decorations | Order of the Cross of Liberty |
&sq=Qlik&lang=&file=File:RUK-risti.jpg)
The Reserve Officer School (Finnish: Reserviupseerikoulu, RUK), located in Hamina, Finland, near the southeastern border, is responsible for the training of most Finnish reserve officers.