The 34-year-old has played in just one Premier League game this season, the opening-day destruction of QPR, and moves to the Valley in search of regular playing time
The 34-year-old will remain at the Championship side until May 4, having made only three appearances under Michael Laudrup for the Swans this season.
Charlton currently sit in 12th place in the table, 10 points adrift of the play-off places.
Gower trained with his new club Thursday morning, and is available for selection immediately ahead of the Addicks’ encounter with Millwall at the Valley on Saturday.
The former Tottenham and Barnet man first came to the Liberty Stadium in 2008 and played a crucial role in earning Swansea a trip to the play-off final in 2011 that ultimately saw the club make its Premier League debut last season.