The French-Congolese centre-back, 21, found himself squeezed out at Villarreal following Juan Foyth's return from injury, leaving the club with a surplus of options in central defence.
After failing to feature in Villarreal's opening match of the season, Kambwala has opted to accept a temporary move to Pamplona in search of the regular minutes he would otherwise have struggled to find at La Ceramica.
According to Marca, Villarreal had been working to find a new home for the defender after completing Thiago Fernandez's loan to Levante, with the Osasuna proposal viewed favourably by the club's hierarchy. The final decision rested with Kambwala himself, who deliberated over his immediate future before settling on the move.
Kambwala joined Villarreal from Manchester United in the summer of 2024 for a reported €10million and remains under contract until June 2029. His progress at the club was disrupted last season by a serious muscular injury that required surgery and limited him to a small number of appearances. With Renato Veiga, Foyth, Logan Costa and Pau Navarro all also competing for places at centre-back, opportunities at Villarreal this season would have been scarce.
The move gives Osasuna fresh defensive depth as they continue to strengthen their squad for the coming campaign, with the loan expected to be finalised once the clubs formalise the paperwork.
Kambwala made his senior breakthrough at Manchester United, debuting in the Premier League against West Ham United in December 2023 before starting against Liverpool at Old Trafford the following April.
His switch to Villarreal followed shortly afterwards, and while his first season in Spain yielded 19 La Liga appearances, last term was largely wiped out by injury, with his return delayed until a brief reappearance in May.
Osasuna's head coach, Luis Miguel Ramis, has been keen to add competition at the back this summer, and Kambwala's physical profile — he stands at 1.92m — was seen as a natural fit for an Osasuna side that has often relied on defensive solidity to compete in La Liga.