West Belfast Sinn Fein assembly member Michael Ferguson has died suddenly, the party has said.
Michael Ferguson had been suffering from cancer
Mr Ferguson, 53, who was also a councillor in Lisburn, had been treated for testicular cancer.
The father-of-four was diagnosed with the disease two months ago and had undergone a course of chemotherapy.
Sinn Fein president Gerry Adams said: "No one who met Michael could fail to see his passion for life and determination."
Mr Adams extended his sympathies to Mr Ferguson's family adding: "Despite his illness, Michael's death will come as a great shock to the many people who knew and respected him."
Mr Ferguson died on Sunday night.
He had spoken about his illness to the Irish News newspaper last week. The article was published in Monday's edition.
He told the paper: "Men are neglectful of their own health and do not visit their doctors.
"I was squeamish, embarrassed and shy about going to the doctor and asking him to examine my testicles."
Mr Ferguson, who was elected to the assembly in 2003, said he became aware he was unwell last September.
"I went to my GP and was told I was OK. It would take another nine months and a return visit to the doctor before the cancer was found," he said.
Mr Ferguson had been a councillor for the last 18 years.
SDLP Lisburn councillor Patricia Lewsley said she was saddened by Mr Ferguson's death.
"Michael was a colourful character who will be missed by many members of the political family," she said.
"He was honest and straight-forward and I can truly say that he was somebody I could always work well with on bread and butter issues despite our considerable political differences."
Ulster Unionist assembly member Billy Bell extended his sympathies to Mr Ferguson's family.
"From our time on Lisburn Borough Council I knew Michael to be not only an energetic political opponent, but more importantly he was a dedicated family man.
"Michael's brave decision to go public in a bid to raise awareness over the nature of his illness also says much about his personal qualities," Mr Bell said.
Frank Bunting, the northern secretary of the Irish National Teachers'
Organisation, also paid tribuite to Mr Ferguson.
"He was a committed campaigner to progressive educational causes, but the interests of children were always his central motivation," Mr Bunting said.
"He will be sadly missed by all his friends in the education community."