The first season of the South Korean dystopian survival thriller television series Squid Game was created by Korean writer and director Hwang Dong-hyuk. It was released on Netflix on September 17, 2021.

The season stars Lee Jung-jae, Park Hae-soo, O Yeong-su, Wi Ha-joon, Jung Ho-yeon, Heo Sung-tae, Anupam Tripathi and Kim Joo-ryoung. It revolves around a secret contest where 456 players, all of whom are in deep financial hardship, risk their lives to play a series of deadly children's games for the chance to win a ₩45.6 billion cash prize, ₩100 million per contestant.

The season was released worldwide on September 17, 2021, to critical acclaim and international attention. It became Netflix's most-watched series and the most-watched program in 94 countries, attracting more than 142 million member households and 1.65 billion viewing hours in its first four weeks, surpassing Bridgerton as the service's most-watched show. It received numerous accolades, including a Golden Globe Award for O, and Screen Actors Guild Awards for Lee and Jung, respectively; all three were also the first Korean actors to win in those categories. The first season received 14 Primetime Emmy Award nominations, including for Outstanding Drama Series, making it the first non-English-language work to be nominated in this category; Lee won for Outstanding Lead Actor, the first for an Asian actor in a non-English part.

A second season was released in December 2024, followed by a third and final season in June 2025.

Numbers in parentheses denote the character's assigned player number in the Squid Game universe.

Around 2008, Hwang Dong-hyuk had tried unsuccessfully to get investment for a different movie script that he had written, and he, his mother, and his grandmother had to take out loans to stay afloat, but still struggled amid the debt crisis within the country. He spent his free time in a Manhwabang (South Korean manga cafe) reading Japanese survival manga such as Battle Royale, Liar Game and Gambling Apocalypse: Kaiji. Hwang compared the characters' situation in these works to his own current situation and considered the idea of being able to join such a survival game to win money to get him out of debt, leading him to write a film script on that concept throughout 2009. Hwang stated, "I wanted to write a story that was an allegory or fable about modern capitalist society, something that depicts an extreme competition, somewhat like the extreme competition of life. But I wanted it to use the kind of characters we've all met in real life." Hwang feared the storyline was "too difficult to understand and bizarre" at the time. Hwang tried to sell his story to various Korean production groups and actors, but had been told it was too grotesque and unrealistic. Hwang put this script aside without any takers, and over the next ten years successfully completed three other films, including the crime drama film Silenced (2011) and the historical drama film The Fortress (2017).

In the 2010s, Netflix had seen a large growth in viewership outside of North America, and started investing in productions in other regions, including Korea. In 2018, Ted Sarandos, co-CEO of Netflix, stated that they were looking for more successes from overseas productions: "The exciting thing for me would be if the next Stranger Things came from outside America. Right now, historically, nothing of that scale has ever come from anywhere but Hollywood." Netflix had opened up a division in Asia in 2018, and while they were still operating out of temporary leased office space in Seoul, Hwang brought his script to their attention. Kim Minyoung, one of Netflix's content officers for the Asian regions, recognized Hwang's talent from The Fortress and his other films, and upon seeing his script for Squid Game, knew they needed it for the service. Kim said "[W]e were looking for shows that were different from what's traditionally 'made it,' and Squid Game was exactly it". In September 2019 Netflix formally announced that they would produce Hwang's work as an original series. Netflix's Bela Bajaria, head of global television operations, said of their interest in Hwang's work that "we knew it was going to be big in Korea because it had a well-regarded director with a bold vision", and that "K-Dramas also travel well across Asia". Regarding his return to the project, Hwang commented, "It's a sad story. But the reason why I returned to the project is because the world 10 years from then has transformed to a place where these unbelievable survival stories are so fitting, and I found that this is the time when people will call these stories intriguing and realistic." Hwang further believed that the COVID-19 pandemic impacted the economic disparity between classes in South Korea, and said that "All of these points made the story very realistic for people compared to a decade ago".

With the Netflix order, the film concept was expanded out to a nine-episode series. Kim stated that there was "so much more than what was written in the 120-minute format. So we worked together to turn it into a series." Hwang said he was able to expand the script so that it "could focus on the relationships between people [and] the stories that each of the people had". Initially, Netflix had named the season Round Six, rather than Squid Game as Hwang had suggested; according to Netflix's vice president for content in Asia Kim Minyoung, while they knew that the name "squid game" would be familiar to Korean viewers from the children's game, it "wouldn't resonate because not many people would get it", and opted to use Round Six as it self-described the nature of the competition. It has been titled as such in Brazil. As production continued, Hwang pushed on the service to use Squid Game instead; its cryptic name and unique visuals helped to draw in curious viewers, according to Kim. At the time that Hwang wrote the season, his goal was to have the season reach the most-watched show in Netflix in the United States for at least one day. Hwang had initially written the season as eight episodes, which was comparable to other Netflix shows, but found that the material for the last episode was longer than he planned, so it was split into two.