Netflix has released a trailer for the upcoming fourth season of smash hit Stranger Things.

The Netflix original sci-fi drama is set to return to the streaming platform after season three ended in the summer of 2019.

Fans of the show have been keeping their eyes peeled for a trailer since the show released a cryptic tweet, teasing a trailer on Wednesday.

Posting on the  official YouTube account HNL Control Room, a video was posted with the caption: "Due to technical difficulties, Hawkins National Laboratory will be closed until further notice. We will be back in service tomorrow at 9:00AM ET."

Now, Netflix has released an official trailer on social media sending fans into meltdown.

The clip shows children playing in what appears to be an asylum with the eerie sound of clocks ticking in the background.

Before a voice says “Good morning, children,” to which a group of children reply “good morning papa.”

The man then asks: ”How are you today?” To which children reply: “Good, Papa.”

He then says: ”Good, I’m glad to hear it. Because today, I have something very special planned for you.”

The camera then pans into a room numbered ‘11’ a nod to the central character of the show played by Millie Bobby Brown.

The screen then goes black as another voice says: “Eleven, are you listening?”

Unfortunately for fans, the trailer does not reveal a release date for the highly anticipated return of the show but that hasn’t stopped fans speculating on social media.

One user tweeted: “Yeah I’m gonna need a release date with this too please Netflix.”

Another user replied with a screen shot from the trailer showing the number three five and six which could be teasing at a June 5 release date.

While other users begged Netflix to reveal the release date.

The return of the series would have inevitably been delayed by the coronavirus pandemic with production halted in March 2020.

Filming resumed in September 2020 and it seems fans won’t have to wait much longer to see how the story unfolds.

It was thought Eleven’s adopted father Jim Hopper, played by David Harbour, was dead following the end of season three, but it seems fan can expect the return of all of their favourite characters.

Showrunners The Duffer Brothers spoke about the upcoming fourth season with Entertainment Weekly last year and teased some exciting moments ahead for fans of the show.

They said: "We're excited to officially announce that production for Stranger Things 4 is now underway—and even more excited to announce the return of Hopper!

"Although it's not all good news for our 'American'; [Hopper] is imprisoned far from home in the snowy wasteland of Kamchatka, Russia, where he will face dangers both human… and other.

"Meanwhile, back in the States, a new horror is beginning to surface, something long buried, something that connects everything..."