Neutrogena has amped up its star wattage with the signing of actress Emma Roberts — on Roberts’ 18th birthday, which was Tuesday.

A week after the Johnson & Johnson-owned brand announced it had signed actress Natascha McElhone as spokeswoman, Neutrogena said Tuesday it signed Roberts as “brand ambassador.”

Referring to Roberts as the newest “face and voice” of Neutrogena, the brand noted that she will join a bevy of celebrities who represent Neutrogena, including Diane Lane, Jennifer Garner, Vanessa Hudgens, Hayden Panettiere, Gabrielle Union, Susie Castillo and Malin Ackerman.

Roberts stated, “It’s important to me to be associated with Neutrogena, because they instill confidence and beauty in young women.”

Details of a national ad campaign in which Roberts is to be featured have yet to be finalized. It could not be determined when ads would break or whether Roberts will represent a particular Neutrogena product.

“Emma Roberts embodies the youthful spirit and confidence that have always been part of Neutrogena,” stated Jim Colleran, president of the Los Angeles-based skin and hair care brand.

Roberts, who became established with the Nickelodeon series “Unfabulous,” stars in the film “Hotel for Dogs,” which is in theaters now.