The 27-year-old, who can play up front or on the wing, has signed a four-year deal to reunite with coach Dick Advocaat, who he played under at PSV Eindhoven and AZ Alkmaar.
Lens had been playing in Ukraine since 2013, winning the domestic cup in his first season and then the league and cup double last season – he was also in Louis van Gaal’s Netherlands squad for the 2014 World Cup and has scored eight goals in his 29 international appearances to date.
Advocaat said of his latest addition: “We have signed an international player and I am delighted to welcome him to Sunderland.
“He is a very well-known player in Europe and has played 29 games for the Dutch national side, which shows his calibre.
“I have worked with him twice already, at PSV and AZ, so I know him well; he is fast and he has scored goals everywhere he has played so that will help the team.”