The moves, announced by the team on Thursday, came two days after the Eagles released cornerback Nnamdi Asomugha in the wake of two disappointing seasons in Philadelphia.
Williams agreed to a three-year deal, and is coming off a big season with the Super Bowl champion Baltimore Ravens. Williams' deal is worth $17 million, including $10.5 million guaranteed, a league source told ESPN NFL Insider Adam Schefter.
Williams started all 16 games, posting four interceptions and 67 tackles. A seventh-round pick of the Tennessee Titans in 2008, Williams joined the Ravens in 2009 and earned a starting role in 2011. Williams, 28, has started all 32 games for Baltimore since 2011.
Phillips comes to Philadelphia on a one-year deal after five seasons with the rival New York Giants. A first-round selection of the Giants in 2008, Phillips, 26, had four interceptions and 72 tackles in 2011, as New York won the Super Bowl. A former Miami Hurricane, Phillips has battled knee injuries throughout his career.
The Eagles, coming off a 4-12 season in which they finished in last place in the NFC East, cut Asomugha, the former All-Pro cornerback, on Tuesday, just two years after he was the NFL's most sought-after free agent. General manager Howie Roseman said he and new coach Chip Kelly spoke to Asomugha and "he took the news with a lot of class."
Asomugha was due to make $15 million this season, including $4 million guaranteed, after signing a five-year, $60 million deal with the Eagles in 2011.
Asomugha signed with the Eagles a year after they won the NFC East in a big summer splash of transactions that appeared to give Philadelphia the inside track to at least a conference title. Asomugha joined defensive linemen Cullen Jenkins and Jason Babin as part of the new-look Eagles defense, and quarterback Vince Young was brought in to back up Michael Vick. There were stars aplenty, on both sides of the field, and it seemed like the sky was the limit for coach Andy Reid's crew.
The Eagles, though, never came close to reaching their potential, missing the playoffs in both seasons, and Reid was fired in January. Philadelphia allowed 444 points last season. Only New Orleans (454) was worse in the NFC. Asomugha had just four interceptions with the Eagles.
Information from The Associated Press and ESPN NFL Insider Adam Schefter was used in this report.