Maguire came to the fore last season as Hull battled against relegation from the top flight, his efforts not enough to stop the club dropping into the Championship.
The 24-year-old will make an immediate return to the Premier League, though, after signing a five-year contract at the King Power Stadium, the two clubs agreeing an undisclosed fee reported to be £17million.
"It's obviously a very exciting time for myself," he told LCFC TV.
"Once I had my eyes on this club, I always wanted to join. Thankfully I'm here so I can't wait to get the season started and kick on.
"There were a number of clubs interested, but when I met the manager here, he pretty much swayed it into the direction of this club. He showed me the way that the club is going. It's on the up and it looks very promising for the future, so credit to the gaffer.
"You can see that with the structure of the club, it's going to look upwards rather than down so that was a big reason why, as soon as I knew there was an interest, I wanted to jump at the opportunity."
Maguire joins a wealth of defensive options at Craig Shakespeare's disposal and will aim to break up the partnership between stalwarts Robert Huth and Wes Morgan.