* Schmidheiny to remain major shareholder
* Spokesman says Schmidheiny supports company strategy
* Former Lafarge Chairman Collomb also to leave board (Adds comment from Schmidheiny spokesman)
By John Revill
ZURICH, April 4 (Reuters) - Thomas Schmidheiny, LafargeHolcim's largest shareholder and a driving force behind the merger that created the world's largest cement maker, will step down from the company's board at its 2018 annual general meeting (AGM), it said on Wednesday.
Schmidheiny, who owns 11.4 percent of the Franco-Swiss company, has decided not to stand for re-election as a board director but will remain a shareholder, it said.
The 72-year-old whose great grandfather Ernst Schmidheiny was one of the founders of its Swiss predecessor, joined the company in 1970 and was chief executive from 1978 to 2001.
He was also chairman from 1984 to 2003, and was instrumental in bringing together France's Lafarge and Switzerland's Holcim to forge the mega-merger in 2015.
"Mr. Schmidheiny is 72 and will be 73 in December. After 40 years in important roles he has decided the time is right to step down, there is nothing else behind this," said his spokesman.
"He has full confidence in Chief Executive Jan Jenisch and the board, and fully supports the current strategy. His departure will not lead to any changes in the company's strategy."
The spokesman said Schmidheiny had no plans to sell his stakeholding and would remain a major shareholder "whatever happens".
Former Lafarge Chairman and Chief Executive Bertrand Collomb will also be standing down from the board at the AGM on May 8, LafargeHolcim said. (Reporting by John Revill; Editing by Michael Shields and Mark Potter)