The river Lakshmanatirtha river is a tributary of the river Kaveri. It originates in the Brahmagiri hills, Kodagu or Coorg and later joins the river Kaveri at Krishnarajasagara.

Originating from the Brahmagiri Range, the river Lakshmana Theertha plungess down from a height of 170 ft. forming the Iruppu Water falls. The Lakshmanatirtha falls or the Irupu falls is a much-visited fresh water cascade located on the river, bordering Kerala, on the way to the Nagerhole National Park. There is a famed Shiva Temple, the Rameshwara Temple, situated on the banks of the Lakshmanatirtha near the falls.

There are many legends surrounding this spot. The most famous is that Rama and Lakshmana reached the Brahmagiri hills, while searching for Sita. When Rama became thirsty, Lakshmana shot an arrow into the hills bringing into being the Lakshmanatirtha river. The sacred origins of the river lend it the power to cleanse away sins and beings devotees in droves during Shivarathri. Like most of the tributaries of Cauvery, this river, particularly the falls is at full capacity during the monsoon.