The Facebook CEO dropped out of Harvard as a sophomore and started up the social network exclusively for college students in 2004.
And just a few years after the site was opened up to the general public in 2006, the 24-year-old CEO landed on the Forbes 400 list of the richest people in America. He ranked No. 321 in 2008, with an estimated net worth of $1.5 billion. At that time, Facebook had about 100 million active users.
Within another year, the number of Facebook users tripled, and Zuckerberg's net worth hit $2 billion.
By 2010, after an investment by private equity firm Elevation Partners valued Facebook at $23 billion, Zuckerberg jumped to No. 35 on the Forbes 400 list, with a net worth of $6.9 billion.
In 2011, Zuckerberg was worth an estimated $17.5 billion, but his fortunes took a turn for the worse in 2012, the same year Facebook went public.
Days after Facebook's IPO on May 18, 2012, shares tumbled on fears that the firm's shares had too lofty a valuation, shrinking Zuckerberg's net worth to just $9.4 billion.
But by last year, as the number of Facebook mobile users and mobile ad revenue continued to grow, Zuckerberg's net worth grew more than it lost the year before.
He was worth $19 billion, according to the latest Forbes 400 list published last fall. And his fortune continues to grow, along with the number of users — 1.28 billion monthly active users as of the end of March. Zuckerberg's net worth is currently estimated at around $26.6 billion.