The 27-year-old can play throughout the back-row and has 39 Check caps for the Pumas to his identify.
A dynamic provider with an impressive work charge, Lezana made his worldwide debut in opposition to France in Paris in 2014 and got here off the bench in Argentina’s historic victory over the All Blacks final 12 months.
He has performed for the Jaguares in Tremendous Rugby and has this season been taking part in for the Pressure in Tremendous Rugby AU.
Lezana, who stands at 6ft 1in and weighs in at 104kg, will present additional choices to the Scarlets back-row and is equally snug at blindside and openside flanker.
Lezana mentioned: “It’s an honour for me to be becoming a member of a aspect with the good historical past and traditions of the Scarlets.
“Having performed in Tremendous Rugby with the Jaguares and Pressure I’m wanting ahead to testing myself in northern hemisphere rugby and taking part in on the prime degree of European competitors.
“Scarlets have some nice gamers within the squad, gamers who I’ve come up in opposition to at Check degree, and I can’t wait to satisfy up with the boys and get began.”
Scarlets common supervisor of rugby Jon Daniels mentioned: “We’re delighted to have secured the signing of Tomas for subsequent season.
“Tomas has performed on the prime degree with the Pumas and in addition has an enormous quantity of expertise in Tremendous Rugby.
“He’s somebody who will give us an additional carrying menace and he’s famend for his excessive defensive stats and work charge.
“With Josh Macleod nonetheless recovering from his Achilles harm and James Davies additionally working his approach again to health, we really feel we would have liked to bolster our back-row sources forward of subsequent season and are wanting ahead to welcoming Tomas to Parc y Scarlets.”
Lezana turns into the Scarlets second signing following the seize of tight-head prop WillGriff John from Sale Sharks.
Scarlets have additionally introduced the re-signing of internationals Wyn Jones, Blade Thomson, Ryan Elias and Aaron Shingler in addition to Carwyn Tuipulotu, Morgan Jones and Javan Sebastian.