Pachimalai Hills are a part of the Eastern Ghats in the southern state of India,Tamil Nadu. The hills are spread over the districts of Tiruchirapalli, Salem and Perambalur. Pachai in Tamil means green and the Pachimalai hills is greener than the some of the hills located nearby. The rivers flowing through the hills are Kallar and Sweata Nadi. The Veeraramar Dam is located in the hills across the Kallar River. The waterfalls in the hills include Mangalam Aruvi, Koraiyar Falls and Mayil Uthu Falls. The most cultivated fruit in the hills is jackfruit.

There are many native tribes inhabiting the hills. The hills are spread over the towns of Thuraiyur, Esanai, Perambalur, Gangavalli, Thammampatti, Arumbavur,Malayalappatti, Thedavur and Uppiliapuram.