Harry Reid was born and raised in Searchlight, Nevada, the youngest of Harry and Inez Reid's four sons. Searchlight is a rural mining town, where Reid's father was a hardrock miner. His father had an eighth grade education, and his mother never completed high school. Reid grew up in a small cabin built from railroad slats without indoor plumbing, and attended a school that employed one teacher for eight grade levels. He attended Basic High School in Henderson—45 miles away—because there was no high school in Searchlight. He boarded with local families in Henderson, so he could be near the school. He was elected student body president and took up boxing. In 2018 he was selected to the Nevada Boxing Hall of Fame.
At Basic High, he met Landra Gould, who became his high-school sweetheart. In 1959, two years after they had graduated from Basic, Harry and Landra were married. They have a daughter, Lana, and four sons, Rory, Leif, Josh, and Key.
After high school, some Henderson businessmen helped to finance a college education for Harry Reid. He also obtained scholarships, and his wife Landra left college to work, so he could attend school. In 1961, Reid graduated from Utah State University. He then earned a law degree from George Washington University. It was at Utah State that Harry and Landra Reid joined the The Church of Jesus Christ of Latter-day Saints, after receiving many years of teaching and example from Church members. During his years as a law student, Reid worked nights as a U.S. Capitol police officer. After law school, the Reid family returned to Henderson, where Reid became the city attorney. He was then elected to the Nevada State Assembly in 1968, at age 28. He became the youngest Lieutenant Governor in Nevada history, elected when he was 30 years old. He then was appointed Chairman of the Nevada Gaming Commission in 1977. He engaged in private law practice for a few years, and then was elected in 1982 to the first of two terms in the United States House of Representatives.
Elected to the Senate in 1986, he has developed a reputation as a consensus builder and a skillful legislator. Orrin Hatch (R-Utah) has said, “We all respect Senator Reid. He is one of the moderate voices around here who tries to get things to work.”
In 1998, he was chosen by his colleagues to serve as the Assistant Democratic Leader, also known as the “Whip.” After he won a fourth term in 2004 by a wide margin, he was unanimously elected Senate Democratic Leader. He is the first Latter-day Saint to serve as majority leader and was the highest ranking elected Latter-day Saint in American History. In spite of his success, he still called Searchlight his home and lived there with his family, when he is not in Washington.
Reid said of his Church membership:
Our blessings are many. We have five children and soon will have twelve grandchildren. All five of our children have attended BYU, and all have been married in the temple. Each child has been a positive example for us.
After these many years I believe that the Church has been a steady, positive blueprint for my life. Without the direction of the Church, I would have been without a compass. 
Reid always kept a copy of the Book of Mormon in his Senate office.
Reid announced on March 27, 2015, that he would not seek reelection in 2016. He was the longest-serving senator in Nevada's history. It is expected that his retirement will “reshape the hierarchy of the Senate Democratic Caucus and upend Nevada’s political landscape.”
On New Year’s Day 2015, Reid was injured while exercising at home, which resulted in broken facial bones and the risk of losing vision in his right eye permanently. In a video he released detailing his decision, he indicated that the “down time” from his injury led him to reflect and conclude that it was time for his retirement. “We’ve got to be more concerned about the country, the Senate, the state of Nevada, than us, and as a result of that, I am not going to run for reelection.”
Reid was diagnosed with pancreatic cancer during a routine screening and had surgery on May 14, 2018, at Johns Hopkins Cancer Center. In February 2019 he announced that due to early detection and chemotherapy, his cancer was in remission. In a June 2020 interview with the Washington Post, Reid said "There's no comparison to how I feel—I feel good. I'm alive." He participated in a new treatment administered by Dr. Patrick Soon-Shiong, an adjunct professor of surgery at UCLA.
Reid died on December 28, 2021. He was 82.
The First Presidency of The Church of Jesus Christ of Latter-day Saints released this statement: “On behalf of The Church of Jesus Christ of Latter-day Saints, we extend our condolences to the family of former Senator Harry Reid of Nevada. Senator Reid was a devoted and capable public servant who was dedicated to his family, his faith and his country. We are grateful for his tireless service in each of these facets of a life well-lived. We pray that Senator Reid’s loved ones will be blessed and sustained at this tender time of parting and in the years ahead.”
Among the speakers at Reid's memorial service was President M. Russell Ballard. Former U.S. president Barack Obama gave the eulogy. U.S. President Joe Biden also spoke, as did Senate Majority Leader Chuck Schumer. Brandon Flowers, one of Reid's favorite musical artists, performed.
Reid was given the J. Reuben Clark Law Society's Distinguished Public Service Award January 20, 2017. The McCarran International Airport in Las Vegas was renamed the Harry Reid International Airport on December 14, 2021.