Kristjan Jaak Peterson, Estonian poet and author (b. 1801)
Kristian Jaak Peterson (14 March [O.S. 2 March] 1801, Riga – 4 August [O.S. 23 July] 1822, Riga) also known as Christian Jacob Petersohn, was an Estonian poet, commonly regarded as a herald of Estonian national literature and the founder of modern Estonian poetry. He died of tuberculosis aged 21.

His birthday is celebrated in Estonia as Mother Tongue Day.