"We are happy to confirm that Maggie and Peter were married on Saturday, May 2," the actress's rep said in a statement to PEOPLE.
The celebration took place in a small chapel in Brindisi, according to European news reports. Among the guests were Jake Gyllenhaal and Reese Witherspoon.
This is the second week in a row that Italy has been the home of a celebrity wedding: April 25 Salma Hayek wed French mogul François-Henri Pinault in a star-studded celebration in Venice.
In March, Gyllenhaal celebrated her impending nuptials with a bridal shower attended by friends, including Witherspoon, a source tells PEOPLE.
Daughter RamonaGyllenhaal, 31, and Sarsgaard, 38, are parents to daughter Ramona, 2 ½. The couple announced their pregnancy and engagement exclusively to PEOPLE in 2006 after being together for more than four years.
The pair costarred in 2003's In God's Hands, a low-budget feature produced by Steven Soderbergh.
Gyllenhaal made her name in the 2002 indie movie Secretary. She recently starred in the blockbuster The Dark Knight, where she replaced Katie Holmes in the role of Rachel Dawes.
Sarsgaard has starred in films such as Kinsey, Jarhead (with his wife's brother, Jake) and Shattered Glass for which he earned a Golden Globe nomination in 2004.