Meilutytė, 16-year-old leader of the Lithuanian national swimming team, defeated seven contestants and covered the distance in 1:04:42.
During the championship semifinals on Monday evening, Meilutytė set a new European, world championship and planet championship record in the event, finishing with a time of 1:04:35 and becoming the first record-holder of the championships.
Meilutytė says that her emotions after the gold medal in Barcelona did not equal to the shock she had during London Olympics last year.
"Of course, the medal is precious, although I was not shocked as I was during the Olympics. A medal always means a lot, it is always an honor to see the Lithuanian flag go up. Yes, the emotions are not as naked as they were on the podium in London, I probably learned to control myself," Meilutytė told journalists in Barcelona after the awards ceremony.
In her words, she was held back by emotions during the Tuesday's swim.
Praise by state leaders
Lithuania's president and prime minister have congratulated Meilutytė on her victory in World Aquatics Championships.
President Dalia Grybauskaitė said that, a year after the Olympic triumph, the swimmer continues surprising the world swimming community and fans of the sport by setting a record after a record and demonstrating determination and strife to swim even faster.
"Dear Rūta, you are in the heart of Lithuania and Lithuania is with you with all its heart. Your determination and confidence in your capacities has united us all," Grybauskaitė said in her congratulatory message.
The president wished Meilutytė success in her other events at the championship.
Prime Minister Algirdas Butkevičius says that Meilutytė's achievements in Barcelona "have awakened Lithuania on holiday and made it happy."
"We are impressed with your talent and determination to win one victory after another, leaving no hope or chance for strong contestants. Dear Rūta, please accept my sincere congratulations on setting a world record and winning the honorable gold medal," Butkevičius said.
"We are proud of your victories and are convinced that you will successfully rewrite the world swimming history and become the best swimmer of all times," the prime minister said in his congratulatory message.