The 27-year-old will join the Premier League champions on a free transfer when his current deal at Sporting Gijon expires.
The 6'0" Spaniard, a former Real Madrid trainee, played 140 games for Gijon, and helped them preserve their La Liga status on the final day of the season, Sporting beating Villarreal 2-0.
Leicester City have announced they will sign the defender Luis Hernández on a free transfer from Sporting Gijón.
Hernandez has made 140 appearances for the La Liga club since making his debut in 2012.
"I am willing to do my best and, above all, I am willing to show gratitude to the club. I am not under pressure at all. It's a challenge for me. Actually, the day I knew Leicester was interested in me, I didn't hesitate.
Leicester have been searching for defensive reinforcements to compete with their established first-choice pair, Wes Morgan and Robert Huth.
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The central defender is a product of the Real Madrid youth academy and moved to Sporting Gijón in 2012. The Madrid-born player helped Sporting beat relegation from La Liga by a point last season, playing 36 times, after they were promoted to the Spanish top flight in 2015.
The 27-year-old joined the Foxes on July 1 after his contract with Gijon expired, signing a four-year deal at the King Power Stadium.
The 27-year-old will join the Premier League champions on a four-year deal when his contract with the Spanish side expires at the end of the month.
They could lose Jamie Vardy after Arsenal triggered his £20m release clause with the striker yet to make any decision public but the Arsenal manager, Arsène Wenger, admitted at the weekend he expected the forward to stay at the King Power Stadium.
Hernandez impressed in the pre-season game against Oxford United and is set to feature against Paris Saint-Germain in the International Champions Cup on Saturday, live on Sky Sports 1 HD from the USA.
Hernandez also revealed that the UK was not the only European country swept up by Leicester's astonishing rise to the top, admitting players in Spain were cheering them on too.
Meanwhile, Burnley have rejected a bid of more than £10m for defender Michael Keane from Leicester City, BBC Radio Lancashire understands.
A statement on the Leicester website said: "With the Foxes set to embark upon their first-ever UEFA Champions League campaign in 2016/17, the addition of Hernandez bolsters what is an already formidable stable of defenders…
"It's a dream for any football player to be part of the Premier League; one of the most followed football competitions in the world. And being part of the actual champion team - it gives me more reasons to be here.
The manager Claudio Ranieri insisted after their title win the club would not chase superstar signings but they have had two bids for Deeney rejected by Watford, the second of £25m coming at the weekend.
Hernandez, 27, will join up with the club on July 1.
"Hernandez has built a solid reputation for himself as a ball-playing defender with an excellent ability to read the game."Hernandez becomes Leicester boss Claudio Ranieri's second signing of the summer following the capture of German keeper Ron-Robert Zieler from Hannover.
"First of all, I have to change my mind. Obviously, the Premier League is much more physical and much more attractive to the audience. I have to adapt myself to this situation. But, as I said, my colleagues' welcome has been wonderful. The manager is also helping me in order to make my adaptation easier."
And he said: "I am very happy to be here with my colleagues. I feel comfortable and the reception has been wonderful.
"Leicester's last season was excellent. Everyone in Spain was watching the team, as it is a small one, but able to fight for the Premier League," he said.
Hernández becomes Leicester’s first summer signing as they prepare for the Champions League next season, while they are also pursuing the Watford striker Troy Deeney.
Find all the latest football transfers on our dedicated page.
"All these efforts contributed to Leicester winning such a complicated competition."
The centre-back is a product of the Real Madrid youth system but failed to make a first-team appearance.
Hernandez, Luis - Leicester (ENG)
"That is why people from Spain have sympathy for the team. It's a beautiful story of a small team that has developed and grown in recent years and, after several seasons, it has managed to gather many good players, a great technical director and the huge support of the citizens.
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He confirmed he would leave the club at the end of the season, writing: "Yesterday I took off [the shirt] for the last time and I feel that these red and white stripes will be stuck to me forever.
"I am with the Premier League's champions and therefore it demands the best of me. It's a challenge for me to be here. I hope to support my colleagues and win every weekend.