| Official Name: | Tremušnjak |
| Settlement Type: | Village |
| Pushpin Map: | Croatia |
| Pushpin Map Caption: | Location of Tremušnjak in Croatia |
| Pushpin Label Position: | bottom |
| Coordinates: | 45.3031°N 16.3086°W |
| Subdivision Type: | Country |
| Subdivision Type1: | Region |
| Subdivision Name1: | Continental Croatia (Banovina) |
| Subdivision Type2: | County |
| Subdivision Name2: | Sisak-Moslavina |
| Subdivision Type3: | Municipality |
| Subdivision Name3: | Petrinja |
| Unit Pref: | Metric |
| Area Footnotes: | [1] |
| Area Total Km2: | 6.2 |
| Population As Of: | 2021 |
| Population Total: | 16 |
| Population Density Km2: | auto |
| Timezone: | CET |
| Timezone Dst: | CEST |
| Utc Offset: | +1 |
| Utc Offset Dst: | +2 |
| Postal Code Type: | Postal code |
| Postal Code: | 44204 Jabukovac |
| Area Code: | (+385) 44 |
Tremušnjak is a village in central Croatia, in the Town of Petrinja, Sisak-Moslavina County. It is connected by the D30 highway.
According to the 2011 census, the village of Tremušnjak had 47 inhabitants. This represents 23.04% of its pre-war population according to the 1991 census.
The 1991 census[2] recorded that 98.53% of the village population were ethnic Serbs (201/204), 0.49% were ethnic Croats (1/204), 0.49% were Yugoslavs (1/204) and 0.49% were of other ethnic origin (1/204).