Former Welsh first minister Rhodri Morgan has died aged 77.
The Labour politician was a "towering figure", former Welsh secretary Lord Hain said.
The current Welsh Secretary, Tory Alun Cairns, said Mr Morgan as a "significant politician" and a "great servant to Wales".
Current First Minister Carwyn Jones said: "Wales has lost a father figure and a great politician tonight."
He said his thoughts were with Mr Morgan's widow Julie.
Lord Hain said: "My deep condolences to Julie and the family on the shock news.
"As first minister Rhodri was both the father of devolution and the father of the nation.
"He did more than anyone to bed down and ensure the new Welsh Assembly gained widespread legitimacy.
"Equally at home both bantering on rugby in a pub or talking economic theory, he was a unique populist intellectual.
"I worked closely with him as secretary of state for Wales to agree the basis for the full law-making powers the Assembly now has.
"He was Welsh through and through and a repository of fascinating facts on everything under the sun.
"A towering figure in every sense whom we will all miss."
Plaid Cymru leader Leanne Wood added her condolences, tweeting: "We have just heard the news that former First Minister of Wales Rhodri Morgan has passed away. Sincere condolences to Julie and the family."
Mr Morgan was first minister for almost 10 years from 1999, before taking up a role as chancellor of Swansea University in October 2011 after retiring from politics.
The university said in a statement: "We are very saddened to hear of his death. Rhodri was a wonderful servant to the university as chancellor, as he was a wonderful servant to the whole of Wales. Our thoughts are with his family and his close friends."