Thibaut Courtois has been embarrassed on the eve of Euro 2016 – by his granddad who came out as a nudist.

The Chelsea keeper, 24, hoped for a calm build-up to Belgium’s trophy quest in France.

But Courtois became the laughing stock of the Red Devils’ camp earlier this week after grandpa Dieudonne appeared naked in a Belgian newspaper to talk about naturism.

The 77-year-old visited a nudist camp near his home and said: “I’ve been a naturist for 50 years. I’ve done it at the seaside in France and a sauna in Holland, and I wanted to see what it’s like without going abroad.”

He even gave a journalist a tour around the camp, and was apparently surprised by the “physical setting.”

Dieudonne added: “I thought it was smaller. I did not know there were so many locations and well-equipped with pool infrastructure. This summer, if the weather permits, I will come to camp a few days.”

The nudist camp is described on its website as being “land perfectly hidden to allow the practice of naturism.”

It also boasts tennis and volleyball courts, a “field of fauna and flora” as well as “many sites” for tents and caravans.

Belgium begin their Euro campaign with a mouth-watering clash against Italy in Lyon on June 13.

But it is nearer to home that Courtois appears to be having a big impact.

Despite a poor season – in which Chelsea claimed the honor of having the worst ever defense of a Premier League title – the keeper could influence transfer plans.

That is because Courtois and Eden Hazard have urged Roma star (and Belgian countryman) Radja Nainggolan to join Antonio Conte’s Stamford Bridge revolution.

Nainggolan — priced at around $40 million — admitted: “Thibaut Courtois and Eden Hazard have already asked me to come to Chelsea, but a possible transfer is not in my head.”