Russian investor Yuri Milner has bought a French chateau-style mansion in Silicon Valley for $100 million, according to a person familiar with the deal. The deal is among the most expensive to have occurred for a U.S. single-family home.

The Los Altos Hills mansion runs more than 30,000 square feet and was completed around 2008, according to an architect who helped design the home. Mr. Milner, who heads Digital Sky Technologies, whose investments include Facebook Inc., Groupon Inc. and Zynga Inc., bought the mansion through...