Twitter's mysterious outside shareholder

Chris Ratcliffe | Bloomberg | Getty Images

Twitter may be having one of the highest-profile initial public offerings in years, but its single largest outside shareholder has almost no online profile.

It's a firm called Rizvi Traverse, and its funds own 17.9 percent of Twitter pre-IPO, 15.6 percent after. It's a bizarre juxtaposition, considering that Twitter's business is based on people's communicating publicly.

But many sources say that Rizvi's low profile helped solidify its relationship with Twitter and secure its access to the company, as well as to other hot start-ups.

Rizvi and its funds have a stake that will be worth $1.7 billion if Twitter's shares are priced at $20—the top of its target range. The firm started investing in the social network at the end of 2010, and its funds have since drawn big-name investors, including JPMorgan, which through its investments will own a 9 percent post-IPO stake in Twitter.

Saudi Prince Alwaleed bin Talal also invested in Twitter through Rizvi, and his Kingdom Holding owns more than 20 million shares.