The teenager made her intentions clear throughout the rounds, setting a new European record in the heats, and was fastest into the final.
Meilutyte led from start to finish and held off a fast-finishing Rebecca Soni, the Beijing silver medallist, to win in 1:05.55.
While the youngster's achievement was the highlight of the night for the crowd, who were clearly moved by what she had done, it was a thrilling night at the Aquatics Centre.
Yannick Agnel won his second, and France's third, gold in 24 hours when he led from start to finish to take the 200m Freestyle title in 1:43.14, the fastest ever in a textile suit.
Talking about France's success in the pool this week, Agnel said 'We are very pleased because it is a reward for several years of very hard work. It's pure happiness.'
Teenager Missy Franklin won her first individual medal when she took the 100m Backstroke title in 58.33, with her fellow American Matt Grevers setting a new Olympic record of 52.16 in the men's equivalent.
Asked about her win, Franklin said 'It's incredible. I dreamt about it all my life and I can't believe it happened at 17 (years old). I cannot put it into words, it's incredible. I still feel like I am in a dream and someone has to pinch me.'