Eduardo was a non-playing member of the Portugal squad that won Euro 2016.
"Having the opportunity to come to the Premier League and to...such a big club, it is an easy decision to make," Eduardo told.
"This is the best and most difficult league and it is another level from where I have been until now. So it is a new challenge."
Eduardo, who will compete with Thibaut Courtois and Asmir Begovic for playing time at Chelsea, becomes new manager Antonio Conte's third signing, following the additions of midfielder N'Golo Kante and striker Michy Batshuayi.
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(Reporting by Shravanth Vijayakumar in Bengaluru; Editing by Tony Jimenez)
