Justices of the Supreme Court on Wednesday thanked Justice Anthony Kennedy for his service as he announced his retirement from the nation's highest court.

Kennedy, 81, told the White House in a letter of his "profound gratitude" for having served for 30 years. He declared his intention to step down as a senior associate justice, to take effect July 31.

WHO ARE THE SUPREME COURT JUSTICES?

Following word of his resignation, Chief Supreme Court Justice John Roberts labeled Kennedy, an "individual of inquestioned independence and integrity," who practiced his legal wisdom not just in Washington, D.C., but "around the world through teaching, lectures, and discussions focused on the rule of law and the necessity of civic engagement."

Justice Clarence Thomas, who served alongside Kennedy for more than 25 years, said Kennedy "has been unfailingly civil and kind in all of his interactions with each of his colleagues. Even during the most difficult and challenging times, he had a way of elevating each of us by his example."

Thomas added that the retiring justice is a "good man who will be remembered not only for a long and productive career on the bench but also for the way he conducted himself."

Kennedy, according to Justice Ruth Bader Ginsberg, "is a true gentleman, a caring jurist, and a grand colleague in all respects." Ginsberg said she'll miss Kennedy and his suggestions, opinions and "his recommendations of art exhibitions to visit with my chambers staff, and much more."

"He has earned a rousing Bravo," Ginsburg said, "for the good he has done during the 43 years he has served as a member of the Federal Judiciary."

"A judge of great vision" who "is thoughtful and careful in his decision-making" were the words Justice Stephen Breyer used to describe Kennedy. He added it was a "great pleasure" for the Supreme Court to work with him.

LAWMAKERS REACT TO ANTHONY KENNEDY'S SHOCKING RETIREMENT NEWS: 'I'M WORRIED ABOUT ROE V. WADE'

Kennedy's "legacy will be of enduring importance," Justice Elena Kagan said. "The Court and country will miss his wisdom, his independence and integrity, his love of liberty and commitment to personal dignity."

"He was the best colleague imaginable," she added.

The retiring justice is "one of the most thoughtful colleagues" Justice Sonia Sotomayor has ever known, according to her statement. "It is undeniable that he has had a monumental effect on the law," the justice added, noting she feels "he will continue to be a roaring lion, even as he takes senior status."

JUSTICE ANTHONY KENNEDY ON THE SUPREME COURT: HIS LEGACY AND THE FUTURE OF HIS SEAT

Neil Gorsuch, the most recent justice to take a seat on the bench following President Trump's appointment of him and Kennedy's former law clark, wrote that Kennedy's "respect for every person and every case has made him a great man and a great judge."

"It has been an unexpected joy to serve this year as his colleague," Gorsuch said, and added Kennedy "is a model of civility judicial temperament, and kindness."

Former Justice John Paul Stevens, who retired from the Supreme Court in 2010, said he and Kennedy have remained close friends since he left, and he "continue[s] to admire [Kennedy's] independence, the high quality of his judicial work, and his devotion to the mission of the Court."

Kennedy was nominated to the Supreme Court by President Ronald Reagan in 1987 and was sworn-in the following year. While often voting with the court’s conservative bloc, he has been a key swing vote in a number of cases and occasionally sided with the court’s liberal wing, particularly on issues such as gay rights and abortion.

His retirement had been rumored in recent years, with several of his former clerks having said they thought he was considering stepping down.

Fox News' Bill Mears and Shannon Bream contributed to this report.