Driussi signed a multi-year, designated player contract after exercising a buyout clause with former club Zenit St. Petersburg.
Additional financial terms were not disclosed, but sources said Driussi's transfer fee was around $7 million and that Austin paid $50,000 to Inter Miami for Driussi's discovery rights.
"I am excited to join Austin FC and continue my career in Major League Soccer," Driussi said.
"I have followed the club in this inaugural season, and I feel honored to represent Austin. The support for Austin FC is world-class, and it was a key factor in my decision to join Austin. I look forward to joining my teammates and coaching staff in making Austin proud and earning positive results."
In accordance with Major League Soccer protocols related to a players' entry into the United States, Driussi will not available for selection for Austin's clash with Colorado Rapids on Saturday.
Austin, who sit in last place in the 13-team Western Conference with 13 points from 14 games, have struggled for goals in its expansion season, averaging less than a goal-a-game. Driussi's arrival is expected to be key to kickstarting the team's attack.
"We are thrilled to welcome Sebastian to Austin," Austin sporting director Claudio Reyna said in a statement. "Sebastian is poised to be an offensive difference-maker in MLS.
"He has represented Argentina's youth national teams, played in the UEFA Champions League, Copa Libertadores, and FIFA Club World Cup in addition to winning 14 trophies so far in his career. This is an impressive resume for any player, let alone at 25 years old. He is a world-class competitor, and we are excited to welcome him to Austin and our club.
"Sebastian comes with an incredible resume. [He's] a competitor, a great teammate, played in Argentina for one of the biggest clubs in River Plate, then moved on to Zenit St. Petersburg and played at a very high level for a team that won championships. So at his age, coming to us, we're really excited to have him. He's going add so much to the team and [his] quality elevates his teammates as well," Reyna said.
"Certainly the role that the atmosphere in the stadium, the training facility, played in recruiting and showing again the ambition that we have to be a serious club in MLS. So he saw that. It's an important step in his career. It's a lot of responsibility. But there's no doubt the enthusiasm, what Austin FC means to the city, was something that resonated with Sebastian.
"We needed extra creativity, extra punch, and courage in the attacking third of the field, and that's exactly what Sebastian brings. He gets in tight areas where you need to be smart and make the right decisions.He gets in those difficult spaces where top players can excel and create chances and that's what you could see was missing, and we felt was missing."
Driussi began his career with South American giants River Plate, making his professional debut at 17 years old in 2013. He went on to make 110 appearances in all competitions, scoring 31 goals. He was also part of the sides that claimed the 2015 Copa Libertadores, the 2014 Argentina Torneo Final, and the 2014 Copa Sudamericana.
Driussi signed for Zenit in a $16.5 million deal ahead of the 2017-18 season, where he went on to make 138 league and cup appearances, scoring 25 goals. During his time in St. Petersburg, the club won three Russian Premier League titles, one Russian Cup and two Russian Super Cups.
"Sebastian is a phenomenal and versatile player who will elevate our attack and make us more dangerous going forward," Austin head Coach Josh Wolff said.
"We've had our eye on him for quite some time. We are confident that Sebastian's international experience and pedigree will raise the level of our entire group and help us compete for a playoff spot this season."
At the international level, Driussi was apart of the Argentina side that won the South American U-20 Championship in 2015. He had also represented the country at the U-17 level.
"This is a wonderful challenge for me in my career, and I can't wait for all of this to start. It's something very wonderful that's about to happen, and I'm looking forward to it," Driussi told reporters.
"I know this is a club that started recently. We all know that. But it's a very interesting project for me. It really grabbed my attention, everything that the club has for me. I definitely want to make history, for this club to make history. And I want to be able to achieve very important things [while] we're here.
"I have a lot of offers from different places, but this was a very attractive and interesting offer for me. Now I know that is exactly where I want to stay. Austin is a club that I want to represent and is like welcome looking forward to playing for them."