The couple filed paperwork in Los Angeles claiming that they split just days after their eighth wedding anniversary in July, according to E! Online.
Attorneys for Hill and Lyn have cited irreconcilable differences as the cause of their separation.
Lyn married Hill in 2004, while the actor was still playing presidential aide Charlie Young on The West Wing.
Hill is currently starring as private detective Burton 'Gus' Guster on the USA Network hit Psych.
Lyn is also an actress, having also appeared in The West Wing and Psych.