The 22-year-old was a key member of the South Korean Olympic squad that took bronze at London 2012, before then going on to make his full international debut in October.
Yun has been linked to a number of clubs in recent times, including west London rivals Fulham, but has joined QPR on for an undisclosed fee from K-League side Chunnam Dragons.
The left-back has been granted a work permit and will be eligible to play for the Rs once he obtains a visa.
Yun joins fellow January acquisitions Loic Remy and Tal Ben Haim at Loftus Road, where he links up with countryman Park Ji-sung.
The defender may be the first of several signings before the transfer deadline, with Peter Crouch, Christopher Samba and Etienne Capoue amongst those on QPR's radar.
Source: PA
Source: PA