FDNY veteran William Moon was remembered at his funeral Thursday as a true hero who continued to help others even in death — with his donated organs saving the lives of two fellow members of New York’s Bravest.

Thousands of uniformed firefighters lined up outside St. Patrick’s Roman Catholic Church in Bay Shore to pay their final respects to Moon, a 47-year-old dad of two who died earlier this month during a training accident at his Brooklyn firehouse.

Moon’s 8-year-old son, Colin, was among them, wearing his father’s dress uniform.

“He describes himself as being cool, being awesome and the smartest in the world,” the youngster, who is aspiring to become a firefighter like his dad, said during the funeral. “My sister says he’s not. I say he is.

“I will never forget how he taught me to roller skate,” the boy said. “My name is Colin Moon and I love him so much.”

Moon’s widow, Kristina, said her husband — a 21-year veteran of the department — was a devoted dad and loving partner whose passion for the fire service was part of the family’s life.

“Some may have already heard me say recently that marrying Billy was like a marriage to the firehouse,” she said. “His dedication and love for the job was intertwined into our daily lives. I have video of the kids responding to their own calls. He wasn’t allowed to leave the house until telling them what he had.

“Many have often heard me say I am raising the female version of Billy in [the couple’s daughter] Brianne and the mini-me version of him in Colin,” she said. “Therefore I know his big personality and strong sense of passion in life will live on as they grow and carry his legacy. Billy, you’re my best friend.”

Moon, a member of the FDNY’s elite Rescue Company 2, was killed on Dec. 12 when he fell 20 feet while training for a skyscraper rescue in Ocean Hill in a tragic freak accident. He was the 1,159th member of New York’s Bravest to die in the line of duty.

His death will save at least five lives, as his family opted to donate his organs.

“Billy donated his organs to save the lives of two firefighters,” Andrew Ansbro, president of the FDNY United Firefighters Association, said outside the Long Island church Thursday.

“Yes, two New York City firefighters, yes,” Ansbro said. “And other people. Even in death, he continued to save lives.”

FDNY Commissioner Laura Kavanagh told mourners that Moon — known as Billy — “exemplified the FDNY in every way.”

“He was the type of person the FDNY attracts and the type of person the FDNY shapes,” she said. “He was not a hero because he was superhuman. He was a hero because he was a man who chose to dedicate himself more fully to those around him every single day.

“Billy’s story isn’t ending today,” Kavanagh said. “It’s a journey.”

FDNY Lt. James Keane said Moon is fondly remembered as a well-liked jokester who was nicknamed by his colleagues “Ichabod Crane,” the well-meaning and gangly hero in Washington Irving’s classic, “The Legend of Sleepy Hollow.”

Keane, who wept as he read the eulogy, noted that Moon’s children are proof of his legacy of giving — Brianne works to help the families of military veterans and Colin is donating his long blonde hair to children who are ill.

“Brianne and Colin, your dad is a real-life superhero,” he said. “All the very best qualities live within you. You have the support of the FDNY and everyone he touched. We will miss your dad, but we will never forget him.”

Rescue 2 is an elite FDNY unit that is trained to respond to the most dangerous emergencies in the Big Apple, including reaching trapped window washers and construction workers buried under collapsed or downed buildings.

Moon began his career with Ladder Company 133 in Queens in 2002, spending 20 years at that house before joining Rescue 2.

He also served as a member of the Islip Volunteer Fire Department on Long Island, serving as chief of that department in 2017.

Moon is survived by his wife, Kristina, and their two young children.

The FDNY Foundation has started an education fund for the children.