Ashley Tisdale and her husband Christopher French have announced they are expecting their first child together.

On Thursday, the High School Musical star, 35, revealed the news on Instagram, where she posted photos showing her cradling her stomach.

In the first photo, Tisdale and French, 38, both dressed in white, are looking down at her pregnant belly, while the second photo sees the couple smiling at each other.

French also shared a photo that appears to be taken on the same day on his own Instagram.

While neither Tisdale nor French captioned the pictures, the reveal prompted an outpouring of congratulatory messages from fans.

“YAY!!!! Luckiest baby in town! Congratulations mama! See you later,” Amanda Kloots commented.

Tisdale’s High School Musical co-star Vanessa Hudgens wrote: “Just the freaking cutest.”

The couple’s announcement comes after they celebrated their sixth wedding anniversary earlier this month.

“Six years. There are so many moments, so many tiny fragile little moments that I can look at specifically. Amazing, beautiful bright ones and hard, cloudy difficult ones ... we just keep getting closer,” French captioned a photo of the couple from their wedding on 8 September 2014. “I really can’t imagine life without you @ashleytisdale. 

"I love you endlessly, happy anniversary.”

Tisdale also shared an anniversary tribute to her husband, writing: “Wow I can’t believe we’ve been married 6 years?!! Time flies. I remember having so much fear the minute we got together because I couldn't believe how good you treated me. I had never been treated that way. But I let go and trusted my heart and eight months later we were a couple of crazy kids engaged.

“Chris you truly have made me a better version of myself because you keep inspiring me everyday. Your heart is pure, you would do anything to make me happy, through the ups and downs you are my solid rock. I’m so grateful I get to be your wife. I love you and after all this time I’m still into you ... PS the last pic is my favourite.”