Scarlets winger Andrew Fenby will join London Irish on a three-year contract at the end of the season.
The 27-year-old has made 75 appearances for the Welsh region since joining from Newcastle Falcons in 2009, scoring 27 tries.
London Irish Director of Rugby, Brian Smith said: "Andrew is a player I have been very impressed with over the last few years.
"He is a physical and abrasive presence who rarely fails to get over the advantage line. He's the second highest try scorer in the RaboDirect, so he knows his way to the try line.
"He will add a further option to our back three for the coming seasons."
Fenby said: "I would firstly like to thank the Scarlets for everything they have done during my time at the club and I wish them well for the future.
"I am looking forward to moving to London Irish and testing myself in the Aviva Premiership. It is a great opportunity for me and I look forward to arriving at the club in the summer."
Scarlets head coach Simon Easterly said the region was grateful for Fenby's contribution during his four seasons in Wales.
He said: "Andy has progressed quickly since joining us and has enjoyed the ability to realise his rugby ambitions from being part of the Scarlets set-up over the past four seasons.
"He has worked hard on his game to establish himself as a regular within our starting line-up more recently.
"He has achieved an impressive try count for us - particularly this season and we know that he will be energetic addition to the team at London Irish.
"He goes with our best wishes and thanks for all he has given to the Scarlets during his time with us."