Siddaramaiah, who led the Congress party to victory in the assembly elections in Karnataka, will take oath as the 22nd chief minister of the state today.
He will be sworn in by Governor H R Bhardwaj at a ceremony at Sri Kanteerava Stadium in Bangalore.
Siddaramaiah, a five-time MLA from Varuna in south Karnataka, was on Friday elected as the leader of the Congress Legislative Party in the state.
The decision in this regard was taken after four AICC observers led by Defence Minister A.K. Antony took the views of newly-elected MLAs on the issue of chief ministership.
Siddaramaiah, who is a backward caste leader from the Kuruba community, met former External Affairs Minister S.M. Krishna for about 20 minutes earlier in the day to seek his support for the coveted post.
Congress made a spectacular comeback in Karnataka wresting power after seven years in its old southern fortress. The party won 121 seats in the 224-member assembly.
The BJP and Janata Dal (Secular) finished second with both winning 40 seats each.
Yeddyurappa's KJP won six seats, while the independents and others won 16 seats.
Elections in Karnataka were conducted for 223 seats. Elections in one constituency - Periyapatna-was deferred to May 28 due to the death of the BJP candidate.