"The governor is pleased to appoint Siddaramaiah as the Chief Minister of Karnataka," the Raj Bhavan office said in a communique.
After meeting Bhardwaj, Siddaramaiah said the governor had invited him to take oath of office soon.
"I will take oath as chief minister most likely on Monday (May 13)," a beaming Siddaramaiah told reporters outside Raj Bhavan.
The appointment came within three hours after Karnataka Pradesh Congress Committee (KPCC) president G. Parameshwara told the governor that Siddaramaiah was unanimously elected as the CLP leader and requested him to invite the latter to form the government.
"After taking oath alone, I will go to New Delhi with Parameshwara and finalise the council of ministers in consultation with the party president Sonia Gandhi and the high command," the chief minister-designate said even as hundreds of his supporters cheered.
On a day of hectic political activity and high drama, Siddaramaiah was named chief minister by the high command after majority of the party's 121 newly-elected legislators preferred him over another aspirant and union Labour Minister Mallikarjun Kharge, who is a Lok Sabha member from Gulbarga, about 650 km from here.
"Siddaramaiah is the choice of the party's high command for the chief minister's post," the party's central observer, Defence Minister A.K. Antony, told reporters at the party's office in the city centre.
Within minutes of the much-awaited announcement, wild celebrations broke out at the party office, with hundreds of cadres and Siddaramaiah's supporters cheering, screaming, hooting and dancing.
"Siddaramaiah has been unanimously selected as our legislature party leader and he will be chief minister," state leader and former minister R.V. Deshpande told reporters even before Antony formally announced the high command's decision.
This was among the quickest decisions taken by the Congress in recent years.
Earlier, all the legislators authorised the high command, which includes party president Sonia Gandhi and vice president Rahul Gandhi, to decide on the name for the coveted post.
"All the legislators have authorised our high command to name the chief minister through a one-line resolution after they expressed their opinion through a secret ballot to the central observers," another party leader, D.K.