He died at the Sarawak Heart Centre in Kota Samarahan this afternoon at 1.25pm from a heart attack.
He would have turned 73 on Jan 27. He was born in 1944.
Adenan, who came back from Australia where he was on a holiday with his family members, was admitted to the Sarawak Heart Centre last Sunday soon after he came back.
In last year's state election, he led the state Barisan Nasional (BN) to a landslide victory, winning 72 out of 82 state seats.
Adenan, who became Sarawak's fifth Chief Minister on February 28, 2014, has a history of heart problems.
Born on January 27, 1944, he took over from long-serving Chief Minister Tun Abdul Taib Mahmud, who is now the state governor.
During his administration, Adenan had strongly pushed for state autonomy.
He initially said late last year that Sarawak BN would table a motion at the state legislative assembly to restore Sarawak's 1963 status as an equal partner to the peninsula, but later decided against it, saying that his administration preferred to use diplomacy.
Adenan was in discussions with Putrajaya on the devolution of power from the federal to the state government.
The Sarawak state government had even issued a moratorium on work permits for Petronas workers from peninsular Malaysia last August following claims of discrimination against Sarawakian staff in the national oil and gas company.
Since becoming chief minister in February 2014, Adenan did what no predecessor has done, starting with taking an oath before the Malaysian Anti-Corruption Commission (MACC) pledging never to award government contracts and allocate state land to his immediate family members.
In the process, he steered away from Taib's administration, who was accused of corruption and abusing his power to enrich family members and crony companies throughout his over 30 years in power.
Altogether, Adenan introduced 53 measures and policies over the last two years, including recognition of the Unified Examination Certificate from Chinese Independent Schools and allocations for Chinese education.
It was these that boosted his popularity among the Sarawakians, including the Chinese community.
Adenan has also won praise for his stand on religious freedom, announcing just before the May 2016 state election that the National Registration Department (NRD) would not challenge a Sarawak Christian's court application to remove the word "Islam" from his MyKad.
Adenan had also made a clear stand against hudud law, directing all Sarawak BN MPs last April to vote against PAS president Datuk Seri Abdul Hadi Awang's private member's Bill on amending the Shariah Courts (Criminal Jurisdiction) Act 1965 (Act 355).
The president of Parti Pesaka Bumiputera Bersatu (PBB) began his political career in 1976 when he was appointed a committee member and the party's legal advisor.
Later in the same year, he contested in elections and won twice — the first in a by-election for the Muara Tuang parliamentary constituency, and in the state election later in the same constituency.
Adenan was an assemblyman for Muara Tuang from 1976 until he moved to Tanjung Datu in 2006 for the state election where he won.
He became the Member of Parliament for the Batang Sadong constituency after the 2004 general election and later was appointed as the Natural Resources and Environment Minister.
He, however, relinquished his ministerial post two years after being in office and returned to Sarawak.
In 2010, he was appointed as Special Advisor to the Chief Minister and later in 2011 as Minister with Special Functions.
The father of five had an illustrious career which included being a journalist, a teacher, a magistrate and a legal adviser prior to his win in Muara Tuang.
He received his legal education at theUniversity of Adelaide in Australia and was once appointed as a public prosecutor in 1969 in Adelaide. He served as magistrate from 1971 to 1972 in Sarawak.
Adenan was appointed as chairman of Sarawak Foundation on Feb 1, 1999 after Taib gave up the post.
His appointment as the Sarawak Chief Minister was also historic, as he was the first leader of Malay descent to hold the post.
Previous chief ministers, Tan Sri Stephen Kalong and Datuk Tawi Sli were of Iban descent while Tun Abdul Rahman Yakub was of Melanau descent.
Taib is also of Melanau descent.