Alex McLeish had been interested in taking him to Birmingham City and Blackburn Rovers were also reported to be keen on securing the Scotland international's signature.
But Boyd, who moves under freedom of contract, now joins fellow Scots Barry Robson, Andrew Halliday and Lee Miller in the north-east of England.
And he will be familiar with ex-Celtic strikers Scott McDonald and Chris Killen, and former Dundee United midfielder Willo Flood, as players Strachan has taken south since his departure from Celtic Park.
Boyd is the Scottish Premier League's all-time top scorer, surpassing former Celtic striker Henrik Larsson's tally of 158 in December last year.
Hignett hails Boyd signing
In October 2008, Boyd said he no longer wished to be selected by George Burley, the Scotland manager at the time, after being used very sparingly in international games.
However, he has since returned to international football, playing for new coach Craig Levein in Scotland's 1-0 win over the Czech Republic in March.
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