'All In Challenge' for COVID-19 relief: Justin Timberlake offers up round of golf and dinner with him and Bill Murray

More and more celebrities are joining in the "All In Challenge," which was kicked off by Fanatics founder and Executive Chairman Michael Rubin on Tuesday.

The challenge is simple: celebrities offer once-in-a-lifetime experiences fans can win by simply donating as little as $10 to COVID-19 relief.

Justin Timberlake isn’t one to back down from a challenge, so when “good friends” Michael Strahan and Ellen DeGeneres approached him to take part, he was more than willing.

The "SexyBack" singer announced in a video posted to his Instagram on Wednesday that he is offering two lucky fans an all-expenses paid trip to the Pebble Beach Golf Resort in Monterey, California, for a round of golf and dinner with him and Bill Murray.

"Roughly 17 million people are in need of food as a result of the coronavirus," he explained. "I want you to join me and everyone else you’ve seen go all in and go in yourself for four important causes."

Justin Bieber decided that, instead of offering up some memorabilia or a role in his next music video, he offered up something else entirely -- himself.

"I am going to auction off a cool experience where I fly to the winner's home and I sing them 'One Less Lonely Girl,'" the "Yummy" singer announced in a video on Tuesday. "I think this can be a cool opportunity and it'll be fun for me!"

In the caption, he added he might just serenade the lucky winner with "a few other" songs, too. He also said he was inspired to donate the experience because many fans have been asking for it.

"Help me feed the hungry during this challenging time," the 26-year-old superstar wrote.

There is no opening bid for the prize. Fans can buy 10 chances for $10 and up to 200 chances for $200. There is no limit on how much money one can donate.

Rapper Meek Mill was so inspired by the challenge that he's parting with his prized possession: his custom matte black 2018 Rolls-Royce Phantom.

"THIS MY BABY IMA MISSSSSSSS YOUUUUUUUUUU," the 32-year-old wrote Tuesday alongside a photo of his beloved vehicle, which is worth over $500,000. "Papers signed!! #donated."

The car, as Mill revealed, shares a deep and personal connection with him, saying it is "my dream car that motivated me to chase success!!"

On the challenge's website, the "Going Bad" artist said he "quickly accepted" the offer to join in. "I'm in a position where I can help out," he explained, taking care to note all the money will go to help out those who have been deeply affected by the COVID-19 pandemic.

The current bid, as of late Tuesday, stands at $300,000. Bidding ends in a little under 13 days.

Actors Leonardo DiCaprio and Robert De Niro are also taking part in the challenge.

The two are offering a chance to score a walk-on role in their upcoming Martin Scorsese-directed film, "Killers of the Flower Moon."

The challenge's website details that the winner will also eat lunch with the cast, attend the red carpet premiere of the film and get some acting tips from Scorsese himself. One donation to this challenge is equivalent to 10 entries. All donations will benefit Feeding America, Meals On Wheels, World Central Kitchen and No Kid Hungry.

As of late Tuesday, the "All In Challenge" has raised over $2,000,000. One hundred percent of the proceeds will be divided between the charities Meals on Wheels, No Kid Hungry and America's Food Fund, who will then disperse the funds to World Central Kitchen and Feeding America.

Other celebrities to join in the challenge included Kevin Hart, Ryan Seacrest, Magic Johnson and many others.