Fritz Karl was born on December 21, 1967, as Karl Friedrich in Gmunden, Austria, and grew up in Traunkirchen by the Traunsee, where his parents ran an inn. Starting in third grade, he attended the boarding school of the Vienna Boys' Choir, which he left at age 13 due to voice change and returned to Traunsee. There, he attended high school, where he played Mephistopheles in a school production of Goethe's "Faust" – a spark for his career as an actor. At 17, Karl left high school and successfully applied for acting studies at the Max Reinhardt Seminar in Vienna, though he left after just two semesters due to "immature behavior."

Karl's career was not hindered by this setback: from 1986, he performed with independent theater groups, appeared at the Vienna Volkstheater, and was engaged at the Theater in der Josefstadt from 1992 to 1997. His first on-screen role was in 1988 in the episode "Die Verlockung" of Dieter Berner's four-part series "Arbeitersaga," playing a teenager planning a visit to Brigitte Bardot with his best friend. In his film debut "Höhenangst" ("Fear of Heights", AT 1994), Karl played the lead role: a young offender who, after serving his sentence, finds a new home on the decaying farm of a reclusive woman. For this role, he was awarded the Max-Ophüls-Preis for Best Young Actor in 1995. A leading TV role followed as a suspect in the "Tatort" episode "Mein ist die Rache" (AT 1996).

Karl's breakthrough came in 1998 with the German-Austrian series "Julia – Eine ungewöhnliche Frau," where he had a regular role as the son of a construction company owner (Franz Buchrieser) until 2001. Simultaneously, he starred as a young Austro-Hungarian officer in Götz Spielmann's adaptation of the Schnitzler novella "Spiel im Morgengrauen" in 2001.

In the following years, Fritz Karl appeared in numerous TV and film productions. In 2003, he portrayed the legendary Bavarian poacher and folk hero Georg Jennerwein in the TV drama "Jennerwein" alongside August Schmölzer and Christoph Waltz. Marcus H. Rosenmüller cast him as the single father of the young protagonist in the successful Bavarian comedy "Wer früher stirbt ist länger tot" ("Grave Decisions", 2006). In the same year, he was seen in the Belgian production "Henry Dunant: Du rouge sur la croix" ("Henry Dunant: Red on the Cross", 2006), a biographical film about the initiator of the Red Cross, as a French officer.

For his leading role as a commissioner in the psychological thriller "Eine folgenschwere Affäre," Karl was nominated for the Bavarian TV Award in 2008. That same year, he starred in the coming-of-age drama "Die Zeit, die man Leben nennt" ("This Life Is Yours") as a divorced father whose son is severely traumatized by an accident. In Xaver Schwarzenberger's "Sisi" (DE/AT/IT 2009), he portrayed Count Andrássy. In 2009, Fritz Karl co-founded the Academy of Austrian Film with other Austrian filmmakers.

Karl's other film roles include a record producer in "Männerherzen" ("Men in the City", 2009) and its sequel "Männerherzen … und die ganz ganz große Liebe" ("Men in the City 2", 2011), a baron in Marcus H. Rosenmüller's "Sommer der Gaukler," the murderer Ami Joe in the Mark Twain adaptation "Tom und Hacke" (2011), the bustling head waiter Leopold in "Im weißen Rössl – Wehe Du singst!" (DE/AT 2013), an obedient citizen in the Kafkaesque science fiction film "Life Guidance" (AT 2017), and the father of the young protagonist in the East-West love story "Zwischen uns die Mauer" ("The Wall Between Us", 2019).

Primarily, however, Karl appeared in numerous television productions, usually in leading roles. From 2014 to 2018, he held the title role in the crime series "Inspektor Jury." Other examples include the police thriller "Unter Feinden" (2013, as an investigator) and its sequels "Zum Sterben zu früh" (2015), "Reich oder tot" (2018), and "Alles auf Rot" (2021). He also appeared in the biographical films "Käthe Kruse" (2015, as Max Kruse) and "Aenne Burda – Die Wirtschaftswunderfrau" (2018, as Franz Burda), as well as the relationship drama "Sugar Love" (2021, as an unfaithful husband). For his leading role as a resistant miner in the Nazi drama "Ein Dorf wehrt sich" ("Secret in the Mountain", DE/AT 2019), he received the Austrian TV award Romy as Most Popular Actor in 2020. From 2022, Karl took on various roles in the successful "Landkrimi" series.

On the big screen, Fritz Karl was seen in the Austrian gangster comedy "Hades - Eine (fast) wahre Geschichte aus der Unterwelt" in 2023 as an inspector and in Joachim Lang's "Führer und Verführer" ("Führer and Seducer") in 2024 as Adolf Hitler.