| Conflict: | Siege of Kalmar |
| Partof: | the Kalmar War |
| Date: | May 3 - August 3, 1611 |
| Place: | Kalmar, Småland, Sweden |
| Result: | Danish victory |
| Commander1: | Bo Bååt Jakob Snakenborg Peder Hammarskjöld |
| Commander2: | Christian IV Sven Sehested |
| Strength1: | 770 foot soldiers 100 cavalry 200-400 armed city residents |
| Strength2: | 4,500 foot soldiers 1,200 cavalry Later on 7,000 men |
| Casualties1: | 700 dead |
| Casualties2: | 200 dead |
The siege of Kalmar occurred in 1611 during the Kalmar War and constituted the major part of an intensive conflict between Denmark–Norway and Sweden for control of the strategically important city of Kalmar and its castle. For centuries, Kalmar was, from a strategic point of view, considered 'to be the key to Sweden'. The country that was in charge of the city with its fortified castle would reign over the Kalmar Strait and have free access to the north, along the Swedish east coast towards Stockholm. From this southern fulcrum in Sweden, a land-based attack against Danish territory and a naval attack with the Swedish navy could have been made possible.
The battle of Kalmar occurred during the summer in the same year.