No actress Katie Holmes is not a Jew. She was a Catholic, then a Scientologist and now, again, a Catholic, as the Examiner reports: Katie Holmes ditches Scientology, Tom Cruse; rejoins Catholic Church.
Wikipedia reports that she is quite Catholic, "Holmes was baptized a Roman Catholic and attended Christ the King Church in Toledo. She graduated from the all-female Notre Dame Academy (also her mother's alma mater), where Katie was a 4.0 student. At St. John's Jesuit, a nearby all-male high school, Holmes appeared in school musicals, playing a waitress in Hello, Dolly! and Lola in Damn Yankees."
She inches just a tad towards Jewish with these accomplishments, "She scored 1310 out of 1600 on her SAT and was accepted to Columbia University (and attended for a summer session); her father wanted her to be a doctor."