The Wales international, reports BILD, will join the Potters on-loan to the end of this season. However, no permanent option will be included.
Matondo is tied to S04 to 2023 and there is hope he will find some regular football and form with the Championship outfit.
The former Manchester City youth teamer was also interesting Brighton, but it's understood regular football was the priority for the player at this stage in his career.
Matondo has managed just the three first team appearances for S04 this season.