| Official Name: | Joniškis |
| Settlement Type: | Town |
| Pushpin Map: | Lithuania |
| Pushpin Label Position: | Location in Lithuania |
| Subdivision Name: |  Lithuania |
| Subdivision Type1: | County |
| Subdivision Name1: | Utena County |
| Subdivision Type2: | Municipality |
| Subdivision Name2: | Molėtai District Municipality |
| Subdivision Type3: | Eldership |
| Subdivision Name3: | Joniškis eldership |
| Population As Of: | 2011 |
| Population Total: | 258 |
| Timezone: | EET |
| Utc Offset: | +2 |
| Timezone Dst: | EEST |
| Utc Offset Dst: | +3 |
| Coordinates: | 55.0669°N 25.6581°W |
Joniškis (Polish: Janiszki) is a small town in Utena County, Lithuania. According to the 2011 census, the town has a population of 258 people.[1]
During the period when Lithuania was independent (1918-1940), there were about 200 local inhabitants, the majority of whom were Poles and Jews.
In June 1941, the German army occupied Joniškis. More than 120 local Jews from the village were shot in pits near Lake Arinas. Men and women were first gathered in a barn and then separated before the shooting. In one of the mass graves, near the cemetery, about 60 men were executed. In the other one, right on the bank of Arinas, 85 female and children corpses were found. Jewish shops and houses were looted by the shooters right after the execution.[2]