The winger is the first Glasgow Warriors player to receive a nomination since 2017, when Finn Russell and Stuart Hogg - who ultimately won the award - were both shortlisted at the end of the competition.
Steyn featured in all five of Scotland's matches, playing a key role in helping his side secure a third-place finish.
He led the tournament in defenders beaten, with a total of 26 - six more than fellow nominee Tommaso Menoncello.
The winger also scored three tries, including two in Scotland's 50-40 win over France at Scottish Gas Murrayfield, a result that ended France's hopes of completing a Grand Slam.
His performances earned him Player of the Match awards against both England and France, underlining his influence in the aerial battle and his consistent form, which has also been evident in a Glasgow shirt during the 2025/26 season.
Speaking after the announcement, Glasgow Warriors Head Coach Franco Smith praised his captain, saying: "We see the hard work and dedication Kyle turns in day in, day out at Scotstoun, and he is a true Warrior that is passionate about not only becoming the best version of himself, but also driving the standards of those around him.
"To see his efforts recognised on the international stage for Scotland is testament to him, and everyone at Glasgow Warriors is extremely proud of him."