The 26-year-old made 199 appearances during a five-year spell with the Swans, his last being in the Championship play-off final win over Reading at Wembley which secured promotion to the Premier League.
“We’re delighted to have Darren here,” said Bolton manager Owen Coyle. “A number clubs were interested in him and we are pleased to have secured his services.”
Sylvain Marveaux officially became a Newcastle player after his contract at Rennes expired.
The 25-year-old midfielder agreed a five-year deal with the Magpies last month, but had to wait until yesterday for his move to be completed.
Marveaux, who had previously been linked with Liverpool, is one of four new faces to have arrived on Tyneside since the end of last season along with Yohan Cabaye, Demba Ba and Mehdi Abeid.
Spanish midfielder Borja Valero has made his move from West Brom to Villarreal permanent after initially spending last season on loan at the Primera Division outfit.
Valero, 26, became the Baggies’ record signing when he joined from Real Mallorca for £4.7m in 2008 but he failed to settle.