The agreement will result in significant investment for the game of rugby at all levels within Ulster.
Kingspan, whose global headquarters are in Kingscourt, County Cavan, has been a sponsor of Ulster Rugby since 1999.
Commenting on the announcement in Belfast, Ulster Rugby CEO Shane Logan said: "We are delighted to have extended our partnership with Kingspan, one of Ulster's most successful international companies, and to have secured a stadium naming rights partner for the first time.
"This is a landmark deal and one that will have considerable benefits for all of rugby in Ulster.
"I want to thank Kingspan for its long-term commitment to the province and I look forward to many more special rugby occasions, from school and club finals to European match nights, at Kingspan Stadium in the future."
Pat Freeman, Managing Director of Kingspan Environmental, added: "Both Ulster Rugby and Kingspan are successful globally recognised brands within their respective fields.
"We have been a partner of Ulster Rugby for 15 years and have witnessed the tremendous growth of rugby in the province. We have also had extensive input into the redevelopment of the stadium through our high performance technologies.
"We are delighted to significantly extend our already strong association with Ulster Rugby by putting our name to such a wonderful sporting venue and are proud that the home of Ulster Rugby will be now known as Kingspan Stadium."
John Robinson, President of the Ulster Branch of the IRFU, warmly welcomed the new association when he said: "This long-term deal, with a leading Ulster company, will result in a highly significant investment for rugby in the province and is a contract of which all involved can be very proud.
"Rugby has never been stronger in Ulster and partnerships such as this will enable us to continue to grow the game at club and schools level and to remain competitive both in Europe and the PRO12."
Kingspan Stadium is owned by the Irish Rugby Football Union. It is located in south east Belfast and is the home of rugby in Ulster.
In 2012, Ulster Rugby secured £16.5 million of funding from the Northern Ireland Executive for the redevelopment of the ground. Three new stands were built raising capacity from 11,400 to 18,000.
The stadium hosts the Ulster Rugby squad's professional training base, consisting of a 7,000 square foot gym, meeting rooms and medical facilities.
Kingspan Stadium plays host to at least 15 Ulster Rugby matches a season and up to 30 schools and club rugby activities - from Under-10 Mini rugby to the Senior Cup final.