Prince Henry Daniel Mills (born August 15, 2001, age 29), also known as Henry Swan during the missing year, the Author and the Truest Believer, is one of the main characters in the first six seasons of ABC's Once Upon a Time and is the main protagonist of the series' seventh and final season. Henry is the biological son of Emma Swan and Neal Cassidy, half-brother of Hope Jones, the stepson of Killian Jones, the adopted son of Regina Mills, nephew of Neal Nolan and grandson of Rumplestiltskin, Prince Charming/David Nolan, and Snow White, husband of Ella Mills, and biological father of Lucy.

Born in Phoenix, Arizona, Henry was eventually adopted by Regina Mills and she kept him by changing her mind at the last minute. Growing up in this quaint town of Storybrooke, Henry realized he was the only one who aged and felt that his birth mother did not love him. Being a loner, Snow gave Henry a storybook filled with many of the fairytale characters in order to give her unknown grandson hope. Henry constantly tries to prove to his mother that the curse is real, but she continues to not believe him. Eventually, Henry takes a bite of a poisoned apple turnover that Regina intended to give Emma, and nearly dies, but Emma gives Henry true love's kiss on his forehead. While barely starting a relationship with Emma and his new grandparents, Henry is separated from his mother and grandmother. Throughout their time being gone, Henry's soul travels to the Netherworld due to a side effect of the sleeping curse. They are able to bring Emma and Mary Margaret back home, with Henry embracing them at last.

Meanwhile Regina continues to be a better mother for her son, but ultimately ends up breaking his heart by succumbing to her former magical impulses. He later learned the identity of his birth father, Neal Cassidy when his mother led him to believe that his dad died in a fire saving a family, which caused a rift in Henry's relationship with Emma. After August apparently died, but was resurrected, Emma promised to never lie to Henry again, which made Henry trust her completely again. During the attempted destruction of Storybrooke, Henry spent the last moments with his family but Regina and Emma are able to deactivate the trigger , however, Henry is kidnapped by Greg and Tamara in the mix of it all and is taken to Neverland.

It is learned that he is the Truest Believer, but Peter Pan, his great-grandfather wanted to steal his heart in order to restore his youth. During a brief time, Henry switches bodies with Pan, but switches back. However, after Pan cast the dark curse, Henry and Emma are forced to retreat to the Land Without Magic and live a new life in New York with new memories. A year later, Henry and Emma returned home after Hook gave Emma a potion for