The German plundered 26 goals in 39 league games for Les Unionistes.
The 25-year-old, who was loaned back to Union after completing a €6m move to Albion in January, netted more domestic league goals than Mohamed Salah, Heung-min Son and Erling Haaland during the 2021-22 campaign.
The honour comes after the prolific striker was voted as the Belgian top flight’s player of the season.
Undav, alongside fellow Seagulls loanees Kaoru Mitoma and Kacper Kozłowski, helped fire Les Unionistes to a first-place finish in the Jupiler Pro League’s regular season.
The Brussels-based outfit were unable to win the championship play-offs but secured UEFA Champions League qualification for the first time in the club’s history.
And Undav’s excellent campaign has seen him named in the Belgian top-flight team of the season.
The forward has been picked alongside Union SG teammate, and former Portsmouth defender, Christian Burgess in FIFA 22’s best eleven.
Club Brugge’s Belgian international pair Hans Vanaken and Charles De Ketelaere have also been selected.
Check out the latest Premier League transfer speculation below...
1. Hammers plot Onana raid
West Ham are interested in signing Amadou Onana from Lille, with the French club forced to sell players after missing out on Champions League football. (Foot Mercato)
2. Palace look at Richards
Crystal Palace are looking at Bayern Munich defender Chris Richards but Patrick Vieira’s first priority remains bringing Cheick Doucoure to Selhurst Park from Lens. (Telegraph)
3. MADRID, SPAIN - MARCH 09: Achraf Hakimi of Paris Saint-Germain in action during the UEFA Champions League Round Of Sixteen Leg Two match between Real Madrid and Paris Saint-Germain at Estadio Santiago Bernabeu on March 09, 2022 in Madrid, Spain. (Photo by Angel Martinez/Getty Images)
Chelsea are closely monitoring the situation of PSG defender Achraf Hakimi. (The Athletic)
4. Garner in demand
Leeds United are prepared to battle Everton and Leicester City for Manchester United midfielder James Garner. (The Sun)