The A-lister took to her Instagram Stories Tuesday, where she announced the death of her pet Chocolate Labrador ... who she has had for over a decade.

Alongside a photo of the sweet pup sitting on a welcome mat, Reese praised the animal as the "best family pet and pack leader."

She added ... "We will miss your sweet spirit, Hank."

Reese's daughter Ava Phillippe also paid tribute to the late pooch -- who was named after country singer Hank Williams -- on Instagram. In her tribute, Ava confirmed Hank was 14-and-a-half years old at the time of his death ... though no cause of death was shared.

AP remembered Hank as being full of "pure love" and having a constantly wagging tail.

She continued ... "The job was 'family pet' & he excelled at it. Thanks Hanky for reminding us that every day is the best day ever."'

Reese's son Deacon Phillippe also shared a short and sweet tribute on Instagram, as he posted a photo of himself hugging Hank on his Stories. He described the family pup as "the happiest dog that ever lived."

Hank's death comes almost 4 years after Reese lost a different family pet ... her beloved French Bulldog, named Pepper. Like she did for Hank, Reese penned a poignant tribute for the late pup, who she called a "devoted family member."