Helmut Birkhan (born 1 February 1938) is an Austrian philologist who is Professor Emeritus of Old High German Language and Literature and the former managing director of the Institute for Germanic Studies at the University of Vienna.

Having studied at Vienna under Otto Höfler, Birkhan specializes in Celtic, Germanic, and Indo-European studies, particularly the study of Celtic-Germanic contacts, Germanic linguistics and Medieval German literature from an interdisciplinary perspective, on which he has published numerous influential works. He has taught generations of students at Vienna, as is well known as a popularizer of scholarship for the broader Austrian public, particularly young people. Birkhan has tutored many influential scholars, including Hermann Reichert, Rudolf Simek, Florian Kragl [de], Melitta Adamson, Fritz Peter Knapp [de] and Alfred Ebenbauer, and continues to teach, write and research.

Helmut Birkhan was born in Vienna, Austria on 1 February 1938, the son of Josef Birkhan, a civil engineer, and Maria Müller. After graduating from gymnasium in Vienna, Birkhan studied philosophy, psychology, classical philology and Germanistics at the University of Vienna, and eventually specialized in Germanicstics, particularly Ancient Germanistics. Birkhan received his PhD in 1962 under the supervision of Otto Höfler, with the dissertation Die Verwandlung in der Volkserzählung. Along with Otto Gschwantler, Peter Wiesinger and Erika Kartschoke and other future prominent scholars, Birkhan belonged to a circle of Höfler's favourite students who called themselves the Drachenrunde. Höfler, who is named in Max Weinreich's Hitler's Professors, and Höfler's questionable stances to Nazi ideology, may have had undue influence on the field in post-war Austria. The Drachenrunde teacher's degree of influence on young Germanistik research after WWII, a sensitive topic, has however, been discussed.

Birkhan lectured at the University of Wales from 1961 to 1962. At Wales, his teacher was the prominent Celtologist Proinsias Mac Cana. Since 1963 he lectured at the Institute for Germanic Studies at the University of Vienna as an assistant of Höfler. In Birkhan, Höfler saw the same capabilities for interdisciplinary learning which was characteristic of his own teacher, the famed Rudolf Much. In 1968 Birkhan received the prestigious two-year Humboldt Research Fellowship to pursue further studies at the University of Göttingen, and subsequently studied archaeology with Herbert Jankuhn, Indo-European studies with Oswald Szemerényi, Celtic studies with Josef Weisweiler, and Scandinavistics with Heinrich Beck. In January 1970, Birkhan habilitated in Ancient Germanistics with a thesis on the relationship between Celts and Germanic peoples in classical antiquity.

Birkhan was appointed Professor of Ancient German Language and Literature at the University of Vienna in 1972. He was subsequently appointed managing director of the Institute for Germanic Studies at the University of Vienna. In 1988, Birkhan established Niederlandistik [de] as a distinct course at Vienna, and subsequently secured the appointment of Herbert van Uffelen to teach this subject. In 1997, Birkhan completed an additional habilitation in Celtic studies with the thesis Kelten. Versuch einer Gesamtdarstellung ihrer Kultur. Together with David Stifter, he subsequently established Celtology as a distinct course at Vienna. After Birkhan's retirement, the teaching of Celtology was suspended at Vienna, despite great opposition from students.

For almost half a century, Birkhan has taught generations of students at Vienna, where he has become well known for his breath of knowledge and friendly personality. He has also dedicated himself towards making scholarship available to the broader public, notably appearing as a druid on the children's television program on the Österreichischer Rundfunk. Many scholars of prominence have gained their degrees under the supervision of Birkhan, including Hermann Reichert, Rudolf Simek, Manfred Kern, Florian Kragl [de], Melitta Adamson, Sang Bea Pack, Fritz Peter Knapp [de] and Alfred Ebenbauer.

Birkhan has been a visiting professor at several universities, including the universities of Picardy Jules Verne (1980), Amsterdam (1993–1994) and Antwerp (1994–1995). Birkhan has received many awards for his scholarship, and was in 1990 made an Officer of the Order of Orange-Nassau (1990). He his a member of several distinguished learned societies, including the Maatschappij der Nederlandse Letterkunde (1991), Austrian Academy of Sciences (1994), the Norwegian Academy of Science and Letters (2002) and the Heidelberg Academy of Sciences and Humanities (2005). He has had two festschrift's published in his honor, Ir Sult Sprechen Willekomen (1998), which was edited by Christa Agnes Tuczay, and Kulturphilologie. (2015), which was edited by his former students Manfred Kern and Florian Kragl.

Birkhan retired from the University of Vienna as professor emeritus in October 2006, but continues to teach and research there, and has continued to publish.