Barkley, who has also played for Everton and Chelsea, will join a Villa side who finished fourth in the English Premier League last season and will compete in the Champions League this term.
"Aston Villa is delighted to announce the signing of Ross Barkley from Luton Town," read a club statement announcing the 30-year-old's arrival. "Welcome, Ross."
England Under-21 international Samuel Iling-Junior and Argentinian midfielder Enzo Barrenechea have also joined Villa from Juventus.
Chelsea have signed Barcelona striker Marc Guiu, 18, on a five-year deal which includes a further 12-month option.
Guiu told the club website: "Ever since I was small, it was my dream to play in the Premier League.
"Now I have the opportunity to come here to Chelsea and I will work my hardest to be successful for the club."
Ben Johnson has ended his 17-year stay at West Ham United to join Premier League new boys Ipswich Town.
Johnson, who joined the Hammers at the age of seven, has signed a four-year deal for the Portman Road side who have Socceroos Massimo Luongo and Cameron Burgess on their books.
"Ben is a player who fits the profile we like to bring to the club," manager Kieran McKenna told the Ipswich website.
"He is a young and talented defender with good technical quality, as well as excellent physical attributes.
Johnson made 109 first-team appearances for West Ham, 69 of those coming in the Premier League.
Welcome, Ben Johnson! ✊ — IPSWICH TOWN (@IpswichTown) pic.twitter.com/X4yvYoN59EJuly 1, 2024
Crystal Palace have signed Japan attacking midfielder Daichi Kamada and reunited him with manager Oliver Glasner.
The two-year deal, which is subject to international clearance, comes into force following the end of Kamada's contract at Serie A side Lazio.
Kamada, 27, previously played under Glasner at Eintracht Frankfurt, where he recorded 40 goals and 33 assists in 179 appearances.
Kamada becomes Palace's second summer signing following the arrival of Morocco international Chadi Riad.
Newcastle United have completed the permanent signing of England U21 defender Lewis Hall from Chelsea.
Hall, 19, spent last season on loan at St James' Park and made 22 appearances, scoring two goals.
The Magpies had earlier recruited Greece goalkeeper Odysseas Vlachodimos from Nottingham Forest, with midfielder Elliot Anderson going in the other direction in signing a five-year deal at the City Ground.
Gambia winger Yankuba Minteh, 19, also departed Tyneside to sign a five-year contract at Brighton & Hove Albion.
