He succeeds his younger brother and former Chief Minister H D Kumaraswamy, who resigned from the post after being elected to Lok Sabha from Bangalore Rural constituency.
A meeting of legislature party, also attended by party supremo Deve Gowda, chose Bandeppa Kashempur as the deputy of Revanna, who was Minister of Energy and Public Works in the JD(S)-BJP coalition government.
Venkat Rao Nadagouda is the new whip and Abdul Azim the Secretary of the Legislature Party, Kumaraswamy told reporters after the meeting.
Kumaraswamy said prominent leaders at the meeting also decided to dissolve all the party units from Central to Taluk-level, barring the post of State unit president which he holds.
"Enrollment of members will formally begin on June 15 and in the next three months we aim to enroll at least 10 lakh members," he said, adding the meeting decided to strengthen the organisation.
The process of reorganising the units and announcing new office-bearers would start in three months. Priority would be given to young lawyers and educated youths in rural areas.
Kumaraswamy said he would tour all districts of the state soon, camping in each of them for two days, in a bid to strengthen the party.