The six-member monetary policy committee (MPC) headed by Governor Shaktikanta Das also changed its monetary policy stance to "accommodative" after the economy grew at its slowest in over four years.
This is the third time this year that the central bank has reduced the key lending rates. On February 7 and April 4, RBI cut the repo rate by 25 basis points.
Repo rate is the rate at which the RBI lends money to commercial banks.
In the fourth quarter, India's economy grew just 5.8 per cent, marking a five-year low, according to government data.
RBI also lowered its gross domestic product (GDP) forecast to 7 per cent for the current fiscal.