The celebrities appear in new public service announcements released by 18 in '08, a group that describes itself as a "nonpartisan youth-run organization dedicated to registering, mobilizing and engaging young voters for the 2008 election."
The PSAs were available Monday and Tuesday exclusively on MySpace and will be splashed across the Web starting Wednesday.
"You and I are about to change the world," Wilde announces at the top of the video.
"The stakes are really high this year. Decisions will be made by the next president that will affect our generation's future for decades to come. It has never been more important to get involved now."
"You have choice," Sarsgaard says in his PSA. "You can sit around and wish the world were different or you can listen to the different ideas, think about which one appeals to you most, vote for that person and it will change."
Wilde has appeared on the TV shows "House" and "The O.C." Sarsgaard has appeared in the films "Jarhead," "Boys Don't Cry," "Shattered Glass" and "Garden State."