The Rasina (Serbian Cyrillic: Расина) is a river in south central Serbia. The 92 km long river flows through the Rasina region, gives its name to the modern Rasina District of Serbia, and flows into the Zapadna Morava near the city of Kruševac.
Its historical name is Arsen (Αρσεγα).
The Rasina springs from the southern slopes of the Goč mountain, near the village of Rašovka, southwest of the most famous Serbian spa, Vrnjačka Banja. The river originally flows to the southeast, around the mountains of Željin and Kopaonik, next to the villages of Mitrovo Polje, Bzenica, Pleš, Jablanica, Grčak, Toskići, Budilovina and Milentija. When the Rasina reaches the small town of Brus, it enters the upper Rasina region and continues next to the villages of Tršanovci, Lepenac and Razbojna.
At this point the river reaches the western side of the Veliki Jastrebac mountain, and makes a wide, elbow turn to the north. In this part of the course, the Rasina also makes a southeast border of the Aleksandrovačka Župa region. After the villages of Bogiše and Zlatari, the Rasina has been dammed at the village of Ćelije, with an artificial lake Ćelije (area 4,16 km², volume 51 million m³). The lake is created as a part of the regulation program of the Velika Morava river and the water is also used for the Kruševac city waterworks.
The lower Rasina region is densely populated (villages of Suvaja, Majdevo, Štitare, Grkljane, Šogolj, Šavrane, Gornji Stepoš, Bukovica, Donji Stepoš, Lipovac, Malo Golovode, Donje Golovode), with the administrative center of the Rasina District, Kruševac. In its lower course, the Rasina is followed by a parallel flow of the Pepeljuša river, which flows into the Zapadna Morava separately. Seven kilometers after Kruševac, the Rasina flows into the Zapadna Morava at the village of Makrešane.
The Rasina drains an area of 994 km², belongs to the Black Sea drainage basin and it is not navigable.