Alonso, who has made no secret of the fact that he hopes to someday win the Triple Crown in motorsport (winning the Monaco GP, the Indy 500, and the 24 Hours of Le Mans) said, "I am very excited to participate in the Le Mans 24 Hours for the first time". We tried for Indy past year, came close, but just missed out.
McLaren has said that Alonso's priority will remain F1 - as such he will be forced to skip the Japanese WEC round at Fuji, which clashes with the United States grand prix. The Spaniard will get behind the wheel of the #8 TS050 Hybrid LMP1 vehicle alongside Sébastian Buemi and Kazuki Nakajima and, according to Gazoo Racing, "will compete in all rounds of the 2018-2019 season which do not conflict with his existing Formula 1 obligations".
Fortunately he will have one of the most competitive cars in the WEC as he'll be behind the wheel of Toyota's TS050 Hybrid, which won 5 of the 9 rounds held last season.
McLaren executive director Zak Brown said he was satisfied Alonso's Le Mans commitments would not detract from his main job in Formula One. This year, I have the chance thanks to McLaren to race for the win at Le Mans. As does Anthony Davidson, who is moving over to the role of reserve/test driver to make way for Alonso (and will presumably fill in again when the Spaniard can't make it).
"I am looking forward to working together with, and learning from, Sébastien and Kazuki, who are both very experienced endurance drivers".
"My deal to race in WEC was only made possible through the good understanding and strong relationship I have with McLaren".
One of the WEC rounds he'll be at is the 24 Hours of Le Mans in June, thus fulfilling a lifelong dream of his.
It was not immediately clear which other WEC races Alonso plans to take part in, but his F1 schedule would seemingly allow him to race in Spa on May 5 - one week prior to the Spanish GP - and at Silverstone on August 19 - one week prior to the Belgian GP, also in Spa. Endurance racing is a different discipline compared to single-seaters and it will be an interesting challenge. "I'm very happy that they listened and understood what this means to me. It will be a learning curve for me but I am ready for this challenge and I can't wait to get started".