“Teen Mom” alum Maci Bookout celebrated son Bentley’s 18th birthday via social media on Wednesday, shocking fans.

“And just like that my baby Bentley is 18 years old!” the former MTV personality, 35, captioned a heartwarming Instagram video of the birthday boy through the years, including multiple shots of the teen towering over her.

“Being your mom is the greatest gift of my life, and I’m so proud of you Benny!” she continued. “We’re not done yet, but we sure did that kid, I love you! ❤️” she concluded.

Fans expressed disbelief in the comments over how much the teen, who was first seen as a newborn on “16 and Pregnant” in 2009, has grown.

“How is Bentley 18?! 🥹🥹 he seems like such a sweet young man. You did a good job Maci ❤️,” one wrote.

Another asked, “18?? How? I remember watching him being born 😭😭”

“Omggg where has the time gone🥹 feel like we all grew up with you guys. Maci you did a wonderful job with him!” a third commented.

Bookout, 35, welcomed Bentley in October 2008 with her then-boyfriend, Ryan Edwards.

After making their reality TV debut on “16 and Pregnant,” the pair joined MTV’s original cast of “Teen Mom” in December 2009.

The former couple briefly got engaged the following year but subsequently called it quits.

Bookout went on to marry motocross racer Taylor McKinney in 2016 and the pair share two children — daughter Jade, 11, and son Maverick, 10.

Edwards, for his part, is the father of son Jagger and daughter Stella with ex Mackenzie Standifer, as well as daughter Presley with wife Amanda Conner.

He, notably, was arrested for heroin-related charges in 2018, with Bookout granted a two-year restraining order against him at the time.

In 2021, he was fired from “Teen Mom OG,” which Bentley exclusively told Page Six was a “huge relief.”

Bookout told us in 2022 that she had realized “years ago” that any optimism she had for Edwards to establish a more active role in Bentley’s life was futile. 

“What I hoped would happen or wished would happen, will probably never happen,” she acknowledged. “It’s not up to anyone but Ryan, so I don’t foresee a world where we’re actually co-parenting.”

In March 2023, a judge ordered Edwards to get help for his substance abuse issues after he was arrested for numerous crimes involving Standifer.

In September of that year, Bookout said her son Bentley was “angry” over his father’s substance abuse.

The father and son’s relationship seemed to be improving last year, when Edwards apologized to Bentley for his absence throughout his childhood in an April 2025 episode of “Teen Mom: The Next Chapter.”

Edwards also said he no longer resented Bookout for keeping Bentley from him amid his addiction struggles.

“16 years later, here we are,” he told his son. “I’m sorry it took us so long, but it’s better now than ever. I’d love to spend time with you whenever you want to come over here.”