David Turnbull has left Celtic to sign for Cardiff City on a permanent deal.
The 24-year-old has scored seven goals in 16 league appearances for the Premiership leaders this campaign.
Since making the move to Parkhead from Motherwell in 2020 he has scored 31 goals in 134 games.
He has two Scottish Premiership titles, two Scottish Cups and two League Cups at Celtic.
Hibernian have made their third signing of deadline day with teenager Eliezer Mayenda joining on loan.
The 18-year-old arrives at Easter Road from Sunderland for the rest of the season.
Hibs announced the signing with just 20 minutes remaining before the window slams shut.
Nick Montgomery said: “He’s a powerful, attacking player with lots of energy. who can play both central and wide.
“At 18, he’s already played Championship football and is highly regarded at Sunderland with a big future ahead of him. He will complete our recruitment for January and add more depth and attacking options to the squad.”
Hibernian forward Harry McKirdy has joined Swindon Town on loan.
The 26-year-old, who has recently recovered from heart surgery, will re-join his old side in the fourth-tier of English football for the remainder of the 2023/24 campaign.
He has made 26 appearances for Hibs since his deadline day move to Easter Road in the summer of 2022.
Following his surgery he has been working his way back to full fitness and has taken the opportunity to play regularly back at Swindon Town.
Motherwell have made their second signing of deadline day with under an hour before the window shuts.
Jili Buyabu has signed for the Steelmen on loan from Sheffield United for the rest of the season.
He joins Rangers youngster Adam Devine at Fir Park as Stuart Kettlewell bolsters his squad for the rest of the season.
Adam Idah says he "can't wait to get started" after joining Celtic on loan until the end of the season.
Speaking to Celtic TV, he said: “It’s such a huge club with such a big history behind it and I can’t even put into words what it’s like to be at Celtic.
“My family and my friends are all delighted that I’m here and I just can’t wait to get started. All of us back home support Celtic so it’s huge for me and I’m so excited to be here.
"I want to play games, I want to help this team and the aim for me is to win those two trophies and I want to score a lot of goals for this club."
With just an hour left of the January transfer window Celtic have confirmed the loan signing of Adam Idah.
The 22-year-old Republic of Ireland international joins the Scottish champions from Norwich City until the end of the season.
He has scored seven goals in 12 starts for the English Championship side this season and will compete with Kyogo Furuhashi and Hyeongyu Oh for the centre-forward position at Celtic Park.
With just over an hour left of the transfer window there has still been no news of Adam Idah's move to Celtic.
The Republic of Ireland is expected to have his loan move from Norwich confirmed before the window slams shut at 11.30pm on Thursday.
But there has been no official announcement yet, meaning Hoops fans will need to stay up late for any updates
We will let you know here as soon as any more moves are confirmed in the last hour.
Kilmarnock have confirmed the signing of former Motherwell striker Kevin van Veen.
The Groningen forward has joined on loan until the end of the season.
A statement from the Rugby Park club said: "Everyone at Kilmarnock would like to wish Kevin a very warm welcome."
Inverness Caledonian Thistle have signed Luton Town youngster Aribim Pepple until the end of the season.
The 21-year-old is yet to make a first-team appearance for the English Premier League side and had a short term loan at non-league Bromley Town earlier this season.
Ross County have signed Michee Efete on a short term deal until the end of the season.
The right-back joins the Staggies on a free transfer after leaving Grimsby Town where he has made 18 appearances this season.
The 26-year-old is a former Crystal Palace and Norwich City youngster and has played for DR Congo under-21s.