- The Scotland international full-back was most recently with Kilmarnock, where he played 122 times and was further recognised with 11 national team caps.
The 28-year-old has signed on a short-term deal until the next transfer window
“We’re delighted to add a player of Stephen’s experience,” said manager Stephen Robinson.
“He will give us greater options in both full-back areas, especially at a time where we are lighter on numbers due to injuries.
“He’s an international-level defender who will bring a lot to our squad.”
A youth player with Aberdeen and Celtic, his professional breakthrough came at Partick Thistle, before he moved to Luton Town and then Kilmarnock.
O’Donnell’s contract has the option to extend the deal until the end of the season. He joins subject to Scottish FA clearance.
“I’m delighted to sign a deal with Motherwell,” he said.
“It’s a deal that suits everyone involved. Obviously there’s a few injuries and so the manager was looking for someone.
“When he came to me, I was delighted to sign up.
“I am a local boy, so it’s a great fit for me. And obviously, the chance to have another crack at Europe was a big factor.
“I feel I’ve a lot to prove at that level and to get that chance is important, especially with Scotland games on the horizon too.
“But first, I want to get playing games and help the team.”
