| Official Name: | Vilainiai |
| Settlement Type: | Village |
| Pushpin Map: | Kėdainiai District Municipality#Lithuania |
| Pushpin Map Caption: | Location in Lithuania |
| Subdivision Name: |  Lithuania |
| Subdivision Type1: | County |
| Subdivision Name1: | Kaunas County |
| Subdivision Type2: | Municipality |
| Subdivision Name2: | Kėdainiai district municipality |
| Subdivision Type3: | Eldership |
| Subdivision Name3: | Vilainiai Eldership |
| Subdivision Type6: | Capital of |
| Subdivision Name6: | Vilainiai Eldership |
| Population As Of: | 2021 |
| Population Total: | 1157 |
| Timezone: | EET |
| Utc Offset: | +2 |
| Timezone Dst: | EEST |
| Utc Offset Dst: | +3 |
| Coordinates: | 55.3°N 24.0031°W |
Vilainiai (formerly ru|Вилайни, pl|Wiłajnie) is a village in Kėdainiai district municipality, in Kaunas County, in central Lithuania. According to the 2021 census, the village had a population of 1157 people. It is located next to the north eastern edge of Kėdainiai, on the left bank of the Nevėžis river. There is a kindergarten, a library, a sports school, a culture house, Water Management Institute of Vytautas Magnus University Agriculture Academy.
Vilainiai has been known since 1744. There was a manor and a watermill till the mid-20th century. It developed largely during the Soviet era as a settlement of Land Improvement Institute.