Bo, the Obama family dog, has died, according to the former president.
The black and white Portuguese water dog, who joined the first family in the White House in April 2009, was the last presidential pet before President Joe Biden's dogs, Major and Champ, joined the White House earlier this year.
Bo died of cancer, according to former first lady Michelle Obama.
Barack Obama memorialized the pooch on Twitter, writing, "Today our family lost a true friend and loyal companion. For more than a decade, Bo was a constant, gentle presence in our lives—happy to see us on our good days, our bad days, and everyday in between."
He shared a few photos of Bo, including one of Barack running down the hallway at the White House.
Michelle Obama also remembered Bo on Instagram, sharing a statement signed by the whole family.
"This afternoon was a difficult one for our family. We said goodbye to our best friend—our dog, Bo—after a battle with cancer," she wrote. "For more than a decade, Bo was a constant, comforting presence in our lives. He was there when the girls came home from school, greeting them with a wag. He was there when Barack and I needed a break, sauntering into one of our offices like he owned the place, a ball clamped firmly in his teeth."
"He was there when we flew on Air Force One, when tens of thousands flocked to the South Lawn for the Easter Egg Roll, and when the Pope came to visit," the statement continued. "And when our lives slowed down, he was there, too—helping us see the girls off to college and adjust to life as empty nesters."
Bo, chosen for his hypoallergenic fur, was a gift from late Massachusetts Sen. Ted Kennedy.
The Obamas added a second Portuguese water dog, Sunny, to the family in April 2013.
Bo was about 6 months old in April 2009, according to reports at the time, meaning he was 12 at the time of his death.
On election night in 2008, Barack Obama revealed he had promised daughters Malia and Sasha a dog if he was elected to the White House.
"Sasha and Malia, I love you both more than you can imagine," he said. "And you have earned the new puppy that's coming with us to the new White House."
Michelle Obama's Instagram post referred to the promise: "On the campaign trail in 2008, we promised our daughters that we would get a puppy after the election. At the time, Bo was supposed to be a companion for the girls. We had no idea how much he would mean to all of us."
ABC News' Chris Donovan contributed to this report.