Fleming, aged 31, has represented New Zealand in 85 Test Matches and 226 One Day Internationals scoring in excess of 5,000 Test runs with a highest score of 274 not out versus Sri Lanka.
He was made Captain of New Zealand at the age of 23 in 1997 and mid-way through 2000 he passed Geoff Howarth's record as the most successful New Zealand Captain of all time and led his country to victory in the ICC Champions Trophy.
In the final npower Test match of the 2004 summer Stephen scored 117 against England at Trent Bridge.
Nottinghamshire's Director of Cricket, Mick Newell, said: "It is a real coup for Nottinghamshire to sign the world's leading Captain and one of the best batsmen in international cricket.
"We have built a squad which can be one of the most competitive teams in the country next season.
"Stephen will bring fresh ideas and challenges to our players and will demand international level standards of performance which will help bring out the very best in both our young players and those aspiring for International honours.
"I want to place on record my thanks to Jason Gallian for leading the team to double promotion in 2004 and add that he will play a very important role within the club next summer.
"Jason has enjoyed an excellent season with the bat and I am pleased to announce that we have agreed a new three-year contract with Jason for the 2005, 2006 and 2007 seasons."
Fleming said: "I enjoyed my previous experience of county cricket and have harboured an ambition to captain a leading English county team.
"Nottinghamshire proved they are one of the up and coming counties with double promotion last season and Trent Bridge holds special personal memories with my Test century on the ground this summer.
"The club has developed strong links with New Zealand cricket with Sir Richard Hadlee, Chris Cairns, Daniel Vettori and Nathan Astle having all previously played for them.
"The facilities are world class at Trent Bridge. I was impressed with the ambition and the plans outlined by Mick Newell and I look forward to joining the club in April."
Added Gallian: "The signing of Stephen Fleming shows the ambition of the club and is a clear signal that we intend to challenge for the Championship next season.
"As soon as it became likely that Stephen would sign, the question of the captaincy was discussed.
"As he is arguably the best captain in world cricket, I offered to step down. I have a good few years left and I am sure that I will learn something playing alongside a player of his capability.
"I am pleased to have been offered a three year contract with the club and I have committed my long term future to Trent Bridge by signing this new agreement.
"Even though 2005 is my Benefit Season and a number of exciting events are being planned, this was not really a factor in my decision to step down as captain.
"There is an experienced committee behind the benefit and I will continue to focus on my cricket and score more runs.
"After such a successful season leading Notts to promotion in both competitions, I look forward to being part of a team that will hopefully win more trophies next season."
THURSDAY 21 SEPTEMBER 2017
ENGLAND v WEST INDIES