The 20-year-old has joined the Saint on a season-long loan from German club Augsburg, with an option to buy the centre-back.
The Austria Under 21-international took to the Staplewood grass for the first time in Tuesday's training session.
He returns to England after starting his youth career at MK Dons.
Danso could be in the fray for the side's Premier League trip to Liverpool on Saturday.
— Kevin Danso (@KevinDanso98) August 11, 2019
— Southampton FC (@SouthamptonFC) August 13, 2019