Oskars Kalpaks (January 6, 1882–March 6, 1919) was the commander of 1st Latvian Independent Battalion, also known as "Kalpaks Battalion".

Kalpaks was born to a farming family. Having decided to become a soldier he completed Irkutsk military school and then commenced service with the 183rd Pultusk Infantry Regiment. He displayed talent as a commander and heroism in battle during the First World War and was awarded the most significant Russian military decorations and made Regiment Commander in 1917.

Afer the proclamation of Latvia's independence on 18 November 1918, Kalpaks enlisted with the Ministry of Defence. He organised the defence of Vidzeme against Bolshevik attacks. On 31 December Kalpaks became Commander-in-Chief of all the armed units at the disposal of the Provisional Government of Latvia.

Under his leadership, Latvia's first armed formations became battle capable. On 28 February 1919, Kalpaks was awarded the rank of Colonel. From January to March 1919 the 1st Latvian Battalion fought with the German VI Reserve Corps to repel the Bolshevik raids into Kurzeme and this was the start of Latvia's struggle for liberation. On 6 March 1919 near Airītes, Kalpaks was killed in a skirmish with German Freikorps troops.

After his death, Kalpaks was posthumously awarded Latvia's highest military award, the Order of Lāčplēsis — first, second and third class.

Although never officially assigned to this rank or position, Kalpaks is regarded as the first Commander in Chief of Latvian Armed Forces.