The 2018 edition is the first time that double Formula One world champion Alonso has competed in Le Mans.
The 36-year old Spaniard and team-mates Kazuki Nakajima and Sebastien Buemi secured a two-lap victory.
Twice a Monaco Grand Prix victor, he now wants to win the Indianapolis 500. Win that and he will join the legendary Graham Hill as only the second driver to win the Triple Crown.
Queenslander Campbell, in just his second year of global competition with Porsche, was handed his Le Mans debut over the weekend with a seat in the Dempsey-Proton 911 RSR alongside Christian Ried and Julien Andlauer.
But the Spaniard put in a remarkable stint through the darkness to reduce the deficit and his team mates - both former F1 drivers - did their bit to take back control after dawn had broken over the Sarthe circuit. It later turnout out that Kamui Kobayashi had simply forgotten to pit and was asked to conserve fuel to make it through the lap.
Having dominated qualifying earlier in the weekend, Porsche emerged victorious with its #92 GT Team entry in GTE Pro, with the "Pink Pig" 911 RSR of Michael Christensen, Kevin Estre and Laurens Vanthoor beating its fellow #91 vehicle which finished in second place in the premier GT category. It rejoined the race but retired with engine failure during the final hour. However, as time has shown, having the fastest vehicle is no guarantee of success. It doesn't matter. Only the headline does: Toyota has won the Le Mans 24hrs.
Toyota is the only manufacturer with a team in the World Endurance Championships after the withdrawals of Audi and Porsche in the last two years.
There have been questions about whether it was a demonstration rather than a race, because of the obvious promotional benefits for all involved if Alonso won.
The pair of Rebellion R13 Gibsons were consistently the quickest non-hybrid LMP1 cars throughout the race but, as expected per the regulations, were unable to match the pace of the race-winning Toyota TS050 Hybrids.
Either way, the win is likely only to enhance his status as one of motorsport's iconic historical figures. Will he stop F1 at the end of this year to focus on Indycar totally, or stay in F1 and just do the Indy 500 again next year, as he did in 2017?
He will be back in action for McLaren at the French Grand Prix next week, with the race returning to the calendar for the first time since 2008.