| Conflict: | Siege of Deventer (1578) |
| Partof: | the Eighty Years' War |
| Date: | 3 August – 19 November 1578 |
| Place: | Deventer, Overijssel |
| Territory: | Deventer captured by the States |
| Result: | Dutch victory |
| Combatant1: | States-General of the Netherlands |
| Combatant2: |  German garrison under Spanish command |
| Commander1: | Graaf van Rennenberg Diederik Sonoy |
| Commander2: | Augustyn Ryck Haurincourt |
| Strength1: | Army of Rennenberg: 10 detachments (around 1,300) French army: 1,000 |
| Strength2: | 900 |
| Casualties1: | Unknown |
| Casualties2: | 300 |
The siege of Deventer was a siege of the city of Deventer by States troops under George van Lalaing, count of Rennenberg, from 3 August to 19 November 1578 during the Eighty Years' War. It was besieged in an attempt by the States-General of the Netherlands to better protect the regions of Holland and Utrecht from Spanish plundering. Since 1572 the city had been held by the German Polweiler-regiment for the Spanish Empire on behalf of Don John of Austria. After Lalaing had put into practice a number of pieces of strategic advice from Johan van den Kornput, the city was prepared to negotiate a surrender and on 19 November 1578 handed itself over to States troops.