He is confronting combined outrage over how Russian Federation used Facebook to spread divisive political propaganda during the 2016 USA presidential election and how Facebook seemed unaware that a political consultancy, Cambridge Analytica, improperly harvested personal data of about 87 million Facebook users, a lot of them Americans.
With so much controversy surrounding the social network right now, the questions are likely to be many, the topics varied.
John Thune, Republican chairman of the Senate Commerce, Science, and Transportation Committee, commented: "Our joint hearing will be a public conversation with the CEO of this powerful and influential company about his vision for addressing problems that have generated significant concern about Facebook's role in our democracy, bad actors using the platform, and user privacy".
"We didn't take a broad enough view of our responsibility, and that was a big mistake. Savannah, I'm not going to sit here and say that we're not going to find more because we are".
Still, the world's 2.2 billion Facebook users are getting a rude awakening: They're not the customer; they - and their personal information - are the product.
The 33-year-old tech billionaire will appear before back-to-back panels of the Senate judiciary and commerce committees on Tuesday and will also testify in front of the House committee on energy and commerce on Wednesday. Mark R. Warner, the ranking Democrat on the Senate Select Committee on Intelligence, told WVTF Virginia Public Radio recently.
Last month news of the Cambridge Analytica data breach made headlines after it was determined the company violated its agreement with Facebook by sharing user information.
In his written remarks, Zuckerberg called Facebook "an idealistic and optimistic company", and said: "We focused on all the good that connecting people can bring".
Even Zuckerberg's apologies have been criticized. The testimony to the Congress lawmakers is hence supposed to repose confidence in Facebook as well as fix Zuckerberg's personal reputation as he is the face of Facebook.More news: Black Panther Passes Titanic's Box Office Record
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Across Capitol Hill, lawmakers have been increasingly discussing the possibility that Facebook, Google and Amazon could be sued under long-standing antitrust laws and broken up in the way the Bell System telephone monopoly was divided in the 1980s.
Mr. Zuckerberg acknowledges he was slow to spot Russian "bots" using Facebook to meddle in the 2016 US vote. Facebook says more than 70 million of the affected users are in the US, though there are over a million each in the Philippines, Indonesia and the United Kingdom.
Here are five questions that could shed more light on Facebook's privacy practices and the degree to which it is really sorry about playing fast and loose with user data - or just because its practices have drawn the spotlight.
Marks Zuckerberg has admitted Facebook failed to protect user data and prevent manipulation of its platform. He also said the company is investigating every app that had access to a large amount of information before the company moved to prevent such access in 2014 - something that came too late in the Cambridge Analytica case.
One of Zuckerberg's first meetings on Monday will be with Florida Sen.
"My personal opinion of him was he was forthright and honest to the degree that he could".
For years, Congress took a largely "hands-off" approach to regulating the internet.
"I think it's concerning any time a technology company shares your personal information without permission", said Jeff Friedman, executive director of the Greene County Chamber of Commerce.
This question is perhaps the most important one for Facebook's users, some of whom are unfriending or considering ending their relationship with the Silicon Valley company over the recent revelations.