Norwich sold the Birmingham City academy product to Southampton for a club record fee following Premier League relegation last year, in a deal worth around £11m, which also includes a sell-on clause.
Redmond has scored six goals in 38 games for the Saints this season and recently impressed in the EFL Cup final at Wembley, where Southampton were beaten 3-2 by Manchester United.
The 23-year-old picked up the England Under-21 Player of the Year award in January, after helping the squad win the prestigious Toulon tournament in France last summer and to qualify for this summer’s European Under-21 Championship.
He now progresses to Gareth Southgate’s full squad, after picking up 34 caps for the U21s and a total of 73 caps across the age groups for the Three Lions.
Redmond was brought to Norfolk by Chris Hughton in the summer of 2013 in a deal worth £3.2m and went on to score 13 goals in 123 games for City, including memorable strikes against Ipswich and Middlesbrough in the play-off campaign of 2014-15.