Veteran politician Godfrey Gitahi Kariuki, popularly known as GG, died on Thursday night.
Kariuki, who was Laikipia Senator, died at Nairobi Hospital. He was 78.
Sources at the hospital said he suffered septic shock and did not give more details.
The politician served the public under all the four presidents Kenya has said.
He was minister in the Jomo Kenyatta and Daniel Moi regimes and the only MP in Kenya who served in the first Parliament.
The politician was first elected to Parliament in May 1963 and served uninterrupted for 20 years before losing in the 1983 snap elections.
Kariuki will also be remembered for conducting civic education after the launch of the 2010 constitution.
He moved from village to village in the entire county educating the people on its contents.
Last year, Kariuki indicated he would contest for his seat and resign midway but he was trounced during Jubilee party primaries by John Kinyua.
He is the second leader to die in office in Laikipia, after Ephraim wachira who was majority leader in local assembly. Wachira died on December 12, 2015.
Nyeri Governor Nderitu Gachagua died aged 64 at a London hospital on February 24.