Facebook Inc. could file papers for its initial public offering as early as this coming week, people familiar with the matter said, as anticipation mounts for what is likely to be one of the biggest debuts for a U.S. company.

The deal, seen as defining moment for the latest Web investing boom, could raise as much as $10 billion and value the social network between $75 billion and $100 billion, said people familiar with the matter. A valuation of $75 billion would be below earlier expectations.

The...