Former IRA commander who became 'constructive force'
Democratic Unionist leader Arlene Foster wished Martin McGuinness a speedy recovery and praised his contribution to the "good things" they achieved while in government together.
Mr McGuinness's decision to quit politics comes amid a deep rift between him and Mrs Foster - a row that forced the collapse of the Stormont Executive.
Mrs Foster said: "Martin McGuinness and I have had our political differences and we come from very different angles of vision.
"As deputy first minister for almost a decade, Martin McGuinness has been a major figure at Stormont. While never forgetting the past, I believe the work at Stormont provided the foundations for our relative peace today.
"Despite all that has happened I wish Martin McGuinness a speedy recovery and that he and his wife are able to enjoy time with their family away from the relentless focus of public life."
While stating they did not agree with Mr McGuinness on many issues, both the Taoiseach Enda Kenny and Fianna Fáil leader Micheál Martin wished him well.
Mr Kenny said: "I am sorry to learn that Martin McGuinness has decided not to contest the forthcoming election due to his poor health.
"While Martin and I may not always have seen eye-to-eye on every issue, I readily acknowledge the remarkable political journey that he has undertaken."
Mr Martin said he sought to be a "constructive force" in trying to make the post-Good Friday Agreement institutions work.
Former president Mary McAleese said Mr McGuinness would now be missing from the "front line of politics", describing his contribution to the Peace Process as "enormous".
Foreign Affairs Minister Charlie Flanagan urged the parties in Northern Ireland to emulate Martin McGuinness's political legacy.
He said: "As the holder of a joint office, he fully recognised that his duty was to represent all of the people of Northern Ireland. Through word and deed, Martin sought to reach out to those who - for understandable reasons - would have regarded his past with fear, anger and suspicion."
Northern Ireland Secretary James Brokenshire said: "I thank him on behalf of the government for his work in securing a number of significant political agreements, as well as his service as deputy first minister of Northern Ireland."