Judd turns 51, while Christensen turns 38 and Hudson rings in 40.
Hudson, who turns the big 4-0 also celebrated another milestone this week -- the mom-of-three revealed on Instagram that she's a "couple" of pounds away from reaching her goal post-baby weight.
“Okay my friends, wanted to share! I’m a couple lbs. from goal weight!” Hudson wrote while showing off her abs in a photo. “I’ve done it without stressing on food or working out like crazy although I have been disciplined.”
Judd made headlines recently as well for a more serious reason. The actress opened up about her decision to have an abortion after she was raped.
“I’m very thankful I was able to access safe and legal abortion,” Judd shared last week.
As for Christensen, he just reunited with his "Star Wars" co-star Matt Lanter and shared the photo on Twitter.
Here is a list of other stars celebrating their birthdays today:
Actress Elinor Donahue ("Father Knows Best") is 82. Keyboardist Alan Price of The Animals is 77. Actor Tim Curry is 73. Singer Mark "Flo" Volman of The Turtles is 72. Actor Tony Plana ("Ugly Betty") is 67. Death Row Records co-founder Suge Knight is 54. Country singer Bekka Bramlett of Bekka and Billy is 51. Actress Kim Hawthorne ("Greenleaf") is 51. Singer Luis Miguel is 49. Actress Jennifer Esposito ("Blue Bloods") is 47. Actress Jennifer Taylor ("Two and a Half Men") is 47. Singer Madeleine Peyroux is 45. Actor James Franco is 41. Actress Catalina Sandino Moreno ("Che," ''Maria Full of Grace") is 38. Actress Ali Wong ("American Housewife") is 37. Actress Victoria Yeates ("Call the Midwife") is 36. Drummer Steve Johnson of Alabama Shakes is 34.