The naming of the stand will take place before the match, from which half the proceeds will go towards an educational trust for O'Donnell and wife Eileen's four children.
Motherwell chairman John Boyle said: "We are very pleased that Villarreal, who are an outstanding European team and a great club, accepted our invitation to play at Fir Park in this pre-season match.
"It will be an emotional day for everyone associated with Motherwell as we will be renaming the main stand after Phil and we hope our fans will turn out in their thousands again to salute Phil and to see us play against superb opposition."
O'Donnell died at the age of 35 on December 29 last year, after collapsing on the pitch during Motherwell's home match against Dundee United.
O'Donnell's brother, James, said: "It's a great honour for the main stand to be named after Phil and we appreciate deeply everything that has been done for Eileen and the children by ordinary football supporters and by the club as well."