| Official Name: | Gastilonys |
| Settlement Type: | Village |
| Timezone1: | EET |
| Timezone Dst: | EEST |
| Utc Offset: | +2 |
| Utc Offset Dst: | +3 |
| Population Total: | 228 |
| Population As Of: | 1923[1] |
| Subdivision Type: | Country |
| Subdivision Type1: | Ethnographic region |
| Subdivision Name1: | Aukštaitija |
| Subdivision Type2: | County |
| Subdivision Name2: | Kaunas County |
| Subdivision Type3: | Municipality |
| Subdivision Name3: | Kaišiadorys district municipality |
| Subdivision Type4: | Eldership |
| Subdivision Name4: | Rumšiškės eldership |
| Pushpin Map: | Lithuania |
| Pushpin Map Caption: | Location of Gastilonys |
| Coordinates: | 54.878°N 24.144°W |
Gastilonys is a former village in the Kaišiadorys District Municipality, Lithuania, located 1 kilometer south of Grabučiškės, on the right bank of the Kaunas Reservoir.
The Gastilonys Botanical-Zoological Reserve has been established in the village, where grows.
The village used to be on the right bank of the Neman, east of . In 1959, Kaunas was flooded during the construction of the Kaunas Hydroelectric Power Plant, creating the Kaunas Reservoir.
The name of the village comes from the surname Gastila.[2]