The 6th Infantry Regiment (Lithuanian: 6-asis pėstininkų pulkas), later the 6th Infantry Regiment of the Duke of Pilėnai Margiris (Lithuanian: 6-asis pėstininkų Pilėnų Kunigaikščio Margio pulkas) was an infantry regiment that served in the Lithuanian Army during the Interwar period.
The regiment's soldiers fought against the Red Army from January to June in 1919: at Jieznas (February 10–13), Žiežmariai, Subačius.
On 20 November 1920, the battalion was given the name of the 6th Infantry Regiment of the Duke of Pilėnai Margiris.
In the flag given to the regiment in 1937, the inscription was "Tau, tėvų žeme" (For you, the Land of my Fathers).
In 1939 March, after the German occupation of the Klaipėda region, the regiment moved to Plungė, while its 2nd Battalion was deployed in Telšiai.