Thyago Vieira Lucio (born 7 January 1993) is a Brazilian professional baseball pitcher in the Arizona Diamondbacks organization.

Thyago made his professional debut with the Venezuelan Summer League (VSL) Mariners, pitching to a 4.00 earned run average (ERA) in 12 games.

In 2013, Vieira played for the Low-A Everett AquaSox, pitching to a 4–5 record and 3.84 ERA with 51 strikeouts in 68 innings of work.

[1][2] After an extended spring training in 2016, he joined the High-A Bakersfield Blaze as a reliever, where he worked extensively with pitching coach Ethan Katz.

[3] He began the 2017 season with the Double-A Arkansas Travelers, and also played for the Triple-A Tacoma Rainiers, logging a 4.00 ERA in 41 appearances between the two clubs.

Vieira was promoted to the major leagues for the first time on 14 August 2017, and pitched one shutout inning against the Baltimore Orioles before being optioned to Triple-A the next day.

On 16 November 2017, Vieira was traded to the Chicago White Sox in exchange for international bonus pool money.

[9] On 7 April 2022, following a game in which he had hit Hiroshima Toyo Carp batter Ryan McBroom in the head, Vieira was sent down to Yomiuri's farm team.

[15] Vieira allowed all five batters he faced to reach base on four walks and a three-run triple in the eighth inning of an 11–3 home win over the Boston Red Sox which was his Orioles debut two days later on 27 May.

[23] At the qualifiers for the 2017 WBC, he pitched a single inning of scoreless relief; however, Brazil did not move on to the main tournament.