Leicester City have signed former Tranmere full-back Zoumana Bakayogo on a two-year contract.
The 26-year-old Ivorian was a free agent after leaving Tranmere for whom he made almost 150 appearances and scored five goals.
Foxes manager Nigel Pearson told the club website: "A number of clubs were interested in signing Zoumana this summer and we were one of those that had been monitoring him for a considerable period of time.
"I'm really pleased he's chosen Leicester City. It's important to us that we recruit players, not only with ability, but also with a desire to play for and work hard for this Football Club.
"He's a good player with a great attitude and I'm sure he'll fit in well with the current squad we have."
Bakayogo said: "This is a big club and a big challenge for me, stepping up into the Championship. I've taken the chance, I hope to have a good season this year and do well for the team.
"The Championship is a new league for me so I will have to work hard to catch up to the pace, but I'm looking forward to working with everyone."
The 27-year-old, who captained the Millers to automatic promotion back in April, spent a brief loan spell at the Kassam last season where he scored twice in eight appearances.
After passing a medical he has returned to the U's on a three-year deal.
"I had a great time when I was here last year, so I'm looking forward to pulling on the yellow shirt again," he told Oxford's official website.
"Having fought so hard to get Rotherham up last season, I wasn't planning on playing in League Two again. However, I believe that this time next year Oxford will be a League One side anyway and I'm looking forward hugely to helping make that happen and then moving onwards and upwards with the club from there."
Manager Chris Wilder added: "I'm delighted to have been able to bring Johnny back to the club.
"He is a top-quality defender and is the final piece in our jigsaw. He has had a good pre-season with Rotherham so can come in and hit the ground running."
