McNish, a three-time race winner and reigning FIA World Endurance champion, will serve as Grand Marshal for the 82nd running of the event, while two-time Formula One World Champion and Ferrari factory driver Alonso has been named the race starter.
The Scot, who retired from racing last year, will be tasked with driving the pace car during the formation lap, along with other yet-to-be-announced duties.
Alonso, meanwhile, will wave the tri-colour flag to signal the start of the race. IMSA chairman Jim France had that honor last year.
“I am very happy to have been chosen to start this race,” Alonso told Ferrari.com “because it is one of a handful of races that has defined the history of motorsport.
“I’m keen to check out the details on this type of car. In Formula 1, we have also entered the hybrid era and I am curious to find out more about the working methods and technology involved in this series.”
While not having taken part in the race as a driver, the Spaniard represents Ferrari, which has 14 cars in the field — the most of any manufacturer this year.
Additionally, longtime Corvette Racing program manager Doug Fehan will be awarded the prestigious “Spirit of Le Mans” trophy during race week.
The 24 Hours of Le Mans takes part on June 14-15, with live coverage on FOX Sports 1 and FOX Sports 2.24 Hours of Le Mans, Alan McNish, Fernando Alonso