The superhero immortals film is directed by Chloe Zhao and stars Angelina Jolie, Salma Hayek, Kit Harington, Richard Madden, Kumail Nanjiani and Gemma Chan.
Read more: Chloe Zhao makes history as Nomadland wins big
Sweeping coastal scenes and a sneak peek at the characters' costumes left some fans overcome.
Watch: Marvel unveil teaser trailer for Eternals
One person tweeted: "Thank you MCU for this. The #Eternals trailer is beautiful. Can't wait to see Kit Harington and Richard Madden together again."
Harington and Madden are reunited in the movie after previously playing Jon Snow and Robb Stark in fantasy epic series Game Of Thrones.
Another fan tweeted: "How can I go back to work after this?! I'm so hyped! The trailer is beautiful! This poster is beautiful! My life is beautiful! #Eternals"
Someone else agreed: "Oh my gosh!!! It’s so beautiful!."
One fan added: "yall that trailer was so Beautiful i literally cried while watching it they look so beautiful in their suits #Eternals"
One of the most anticipated parts of Eternals is Jolie in her first MCU role as warrior Thena.
One fan tweeted: "#Eternals will be one of the MCU’s best film & a fan favourite & the trailer looks unbelievably good BUT, Can we talk about Angelina Jolie as Thena? I think she just stole my heart."
Another hit with fans is Academy Award-winning Nomadland director Zhao at the helm of the 26th Marvel film.
One person commented: "I really liked what we saw from the #Eternals trailer. Chloe Zhao is really bringing something special to the MCU."
Eternals follows the story of a group of immortal superheroes, an alien race created by the Celestials and having lived secretly on Earth for more than 7,000 years, who reunite to protect humanity from their evil rivals the Deviants.
It is set after an unexpected tragedy following the events of 2019 film Avengers: Endgame.
A voiceover on the trailer says: "We have watched and guided, we have helped them progress and seen them accomplish wonders.
"Throughout the years, we have never interfered – until now."
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At the end of the trailer, Madden's character Ikaris is asked: "So now that Captain Rogers and Iron Man are both gone, who do you think's going to lead the Avengers?"
He replies: "I could lead them," as his fellow Eternals fall about laughing.
Eternals is due to be released in November.
Watch: Salma Hayek teases highly anticipated Eternals