The actress�s name was found by The Spectator in a searchable database containing more details about the Panama Papers tax avoidance�scandal.
The Harry Potter star turned political activist is named in the Panama Papers, revealing she has interests in a firm based in the British Virgin Islands.
The International Consortium of Investigative Journalists (ICIJ) published data on more than 200,000 entities on its website on Monday evening.
The database contains information on companies, trusts and foundations and users can see networks involving the offshore companies.
But a spokesperson for Ms Watson says she does not use the firm to avoid tax, only for privacy.
The database, released online yesterday, reveals Emma Charlotte Duerre Watson is a shareholder of a company based in the British overseas territory.