Karl Werner Aspenström (13 November 1918 – 25 January 1997) was a Swedish poet.
Born at Norrbärke, he was a member of the Swedish Academy, where he held Seat 12 from 1981 to 1997.
Following his breakthrough in 1949 with Snölegend ("Snow legend") he was considered as one of the leading 20th century Swedish poets, and his poetry have often been compared to the works of the Nobel Prize laureats Harry Martinson and Tomas Tranströmer.
Aspenström claimed that his motivation for writing was "writing for his cat".
He was a friend of Stig Dagerman's.