Macron are already responsible for supplying kits to Swansea C ity and several clubs across Europe, and the Italian firm have described their deal with Leeds as "the flagship of our activity".
Leeds have not confirmed the financial terms of the four-year deal, but it is understood the contract is the most valuable held by a club outside the Premier League.
Chief executive Shaun Harvey said: "This is an exciting partnership for the club. The decision to work with Macron in preference to other international brands who were also interested in supplying kit to Leeds United was easy when we learned that their long-term objectives for the brand complement our own objectives.
"It's a big day for Leeds United football club. Those that have followed Leeds United's recent history know that it's always been hand-to-mouth and year-to-year. This is the first time we've been able to sit down an evaluate where we want to be over a period of time."