The 22-year-old becomes the Cherries' third signing of the summer as the club continue to strengthen their squad before their Premier League and Europa League campaigns.
Bournemouth were keen to add another right-back following the departure of Alex Jimenez, with Juanlu arriving after the signings of centre-back Antonio Silva from Benfica and forward Alvaro Rodriguez from Elche.
The Spanish defender made 109 senior appearances for Sevilla and was also part of Spain's gold medal-winning team at the Paris 2024 Olympic Games.
Juanlu said he was delighted to complete the move and believes Bournemouth is the ideal club to continue his development.
"I am very happy, both for me and for my family," he said. "We had a lot of desire to come here and finally I can say that I am a Bournemouth player.
"It's a very familiar club. I think it's a very positive club to continue to grow as a football player. The city, from what I have seen so far, is wonderful. I think it's a very good place to continue to improve."
The defender also admitted that playing in England's top flight had always been one of his ambitions.
"Everyone has a dream of playing in the Premier League," he said. "I think it's the best league in the world and we all dream of playing here."
Juanlu's arrival is expected to leave head coach Gary O'Neil's squad close to complete ahead of Bournemouth's return to European competition, with reports suggesting the squad is now around 95 per cent ready for the new season.
Bournemouth continue their pre-season preparations on Saturday when they travel to Spain to face Real Betis at the Estadio de La Cartuja in Seville.
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Leeds United have completed the signing of goalkeeper James Trafford from Manchester City on a five-year contract in a club-record deal.
Real Madrid have ended speculation over Vinicius Junior's future after the Brazilian winger signed a new six-year contract that will keep him at the club until June 2032.
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