Cook took to Instagram on Thursday to share the news with a touching video of the Big Bang Theory star crying tears of joy moments after the proposal.
"After nearly two years I finally got up the courage to ask her to marry me," Cook captioned the post. "This is the best night of my life and I think the video shows it is the best night for kaley as well."
The sweet, funny video shows the actress -- who was also celebrating her 32nd birthday on Thursday -- weeping and laughing as she holds up the sizeable new sparkler.
"We're engaged!" Cuoco excitedly announces through tears.
"You still haven't said yes yet," Cook jokes from behind the camera.
"Yes! I say yes! I say yes!" the newly-engaged actress yells as she laughs.
See photos of Kaley Cuoco and Karl Cook together:
Kaley Cuoco and Karl Cook together
Kaley Cuoco and Karl Cook together
SANTA MONICA, CA - JANUARY 11: (L-R) Actor Johnny Galecki, actor Kaley Cuoco, and Karl Cook attend The 23rd Annual Critics' Choice Awards at Barker Hangar on January 11, 2018 in Santa Monica, California. (Photo by Kevin Mazur/WireImage)
WESTWOOD, CA - DECEMBER 17: Actress Kaley Cuoco and Karl Cook arrive at the premiere of 20th Century Fox's 'Why Him?' at Regency Bruin Theater on December 17, 2016 in Westwood, California. (Photo by Gregg DeGuire/WireImage)
NEW YORK, NY - MAY 03: Actress Kaley Cuoco (L) and Karl Cook are seen in the East Village on May 3, 2017 in New York City. (Photo by Gotham/GC Images)
LONG BEACH, CA - SEPTEMBER 29: Equestrian Karl Cook and actress Kaley Cuoco arrive at Longines Masters Los Angeles Gala at Long Beach Convention Center on September 29, 2016 in Long Beach, California. (Photo by Axelle/Bauer-Griffin/FilmMagic)
LOS ANGELES, CA - MAY 02: Karl Cook and Kaley Cuoco is seen at LAX on May 02, 2017 in Los Angeles, California. (Photo by starzfly/Bauer-Griffin/GC Images)
LOS ANGELES, CA - JANUARY 23: Kaley Cuoco and Karl Cook are seen on January 23, 2017 in Los Angeles, California. (Photo by BG015/Bauer-Griffin/GC Images)
BEVERLY HILLS, CA - JANUARY 08: Actress Kaley Cuoco (R) and Karl Cook arrive at the 18th Annual Post-Golden Globes Party hosted by Warner Bros. Pictures and InStyle at The Beverly Hilton Hotel on January 8, 2017 in Beverly Hills, California. (Photo by Axelle/Bauer-Griffin/FilmMagic)
WESTWOOD, CA - DECEMBER 17: Karl Cook and Kaley Cuoco attend the premiere of 20th Century Fox's 'Why Him?' at Regency Bruin Theater on December 17, 2016 in Westwood, California. (Photo by Todd Williamson/Getty Images)
BEVERLY HILLS, CA - JANUARY 08: Actress Kaley Cuoco (R) and Karl Cook attend the 18th Annual Post-Golden Globes Party hosted by Warner Bros. Pictures and InStyle at The Beverly Hilton Hotel on January 8, 2017 in Beverly Hills, California. (Photo by Frazer Harrison/Getty Images)
SANTA MONICA, CA - DECEMBER 11: Actress Kaley Cuoco and Karl Cook arrive at The 22nd Annual Critics' Choice Awards at Barker Hangar on December 11, 2016 in Santa Monica, California. (Photo by Allen Berezovsky/Getty Images for Fashion Media)
SANTA MONICA, CA - DECEMBER 11: Actress Kaley Cuoco and Karl Cook arrive at The 22nd Annual Critics' Choice Awards at Barker Hangar on December 11, 2016 in Santa Monica, California. (Photo by Axelle/Bauer-Griffin/FilmMagic)
LOS ANGELES, CA - DECEMBER 07: Kaley Cuoco and Karl Cook are seen on December 07, 2016 in Los Angeles, California. (Photo by BG002/Bauer-Griffin/GC Images)
LONG BEACH, CA - SEPTEMBER 29: Kaley Cuoco, Karl Cook arrives at the Longines Masters Los Angeles - Gala at Long Beach Convention Center on September 29, 2016 in Long Beach, California. (Photo by Steve Granitz/WireImage)
INDIAN WELLS, CA - MARCH 12: Actress Kaley Cuoco and equestrian Karl Cook react during Bob and Mike Bryan of United States and Rafael Nadal and Fernando Verdasco of Spain doubles match during day six of the BNP Paribas Open at Indian Wells Tennis Garden on March 12, 2016 in Indian Wells, California. (Photo by Kevork S. Djansezian/GC Images)
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Cook also shared a photo of the impressive engagement ring, which features a large, pear-shaped center stone with smaller diamonds lining the band.
"I am so so so happy," he wrote in the caption. "Thank you @nadis_diamonds for making the greatest ring I could hope for. Absolutely brilliant. Thank you thank you."
The ring Cook used to pop the question was nearly as large as the over-sized costume jewelry ring he jokingly presented to his lady love in an Instagram pic shared three hours before he proposed for real.
"On my loves birthday I got her everything she has always wanted," Cook wrote alongside a photo of him and a hilariously annoyed-looking Cuoco in a Target. "Now judging by her face maybe not, it's the thought that counts right."
"He is totally the guy,” she said of the 26-year-old professional equestrian. "I think the common denominator is the horses, it just works for us. We have this special bond so, yeah, the animals. He's so real. I've never met a kinder human being, he's gentle, and he's real. I'm completely in love with him. Nothing could be better."
RELATED: Celebrity weddings rom 2017:
Celebrity Weddings of 2017
Celebrity Weddings of 2017
'Dancing with the Stars' alums Peta and Mak tied the knot on July 8: "07~08~2017 was the most ✨magical✨day of my life. I married my soul mate, my perfect man, the only man I could see myself growing old with," she wrote.
How gorgeous was Peta's dress? Truly one of the most beautiful wedding gowns we saw on any celebrity this year.
Erin Andrew made it official with pro hockey player Jarret Stoll in June.
Samira Wiley and Lauren Morelli, who met on set of 'Orange is the New Black,' celebrated their wedding in March with a service in Palm Springs.
Idina Menzel shared this after her big day: "Wanted to let you know... married the love of my life Aaron Lohr this weekend at our home. Dad & son walked me down the aisle. It was magical. Thank you to everyone who helped make my wedding day so special."
Pippa Middleton married James Matthews at St Mark's Church, Englefield Green on May 20, 2017.
Serena Williams and Alexis Ohanian wed in November in one of the highest-profile celebrity weddings of the year! The "Beauty and the Beast" themed night was nothing short of magical.
"This Is Us" star Justin Hartley looked dapper as ever as he wed Chrishell Stause.
Meghan McCain's father, Senator John McCain, walked her down the aisle during her November ceremony.
Colton Haynes and Jeff Leatham could hardly contain their joy during their big night -- as none other than Kris Jenner presided over the ceremony!
Patton Oswalt and Meredith Salenger wed in November -- and Patton's daughter, Alice, was a big part of the day!
In what easily may have been the most extravagant wedding of the year, Gucci Mane wed Keyshia Ka’oir in a lavish ceremony fit for royalty.
Kate Upton and Justin Verlander wed just days after Justin, a pitcher for the Houston Astros, won the World Series!
We love Clare Bowen's chic but simple ceremony aesthetic. The 'Nashville' star loves a southern charm vibe!
Shay Mooney of Dan + Shay wed his lady, Hannah Billingsley, in a lovely ceremony.
Kacey Musgraves couldn't have looked more beautiful as she wed fellow country singer Ruston Kelly in October.
Alicia Vikander and Michael Fassbender tried to evade the paparazzi by having their ceremony in a private area of Ibiza.
Amanda Seyfried and Thomas Sadoski kept photos of their wedding private -- but no doubt it was stunning!
Miranda Kerr and Evan Spiegel kept most of the details under wraps, but they wed in May. They are now expecting their first child. (Kerr has another child from a previous marriage.)
Alison Brie and Dave Franco wed this year after three years together.