The 2017–18 SM-liiga season was the 43rd season of the SM-liiga (branded simply as "Liiga"), the top level of ice hockey in Finland, since the league's formation in 1975. Tappara was the season as a defending champion. This season included a record number of matches played on Fridays and Saturdays. In autumn, there was a national team break from 5 November until 13 November.
The specialties of the season included, for the first time in SM-liiga history, double games between KooKoo and Vaasan Sport. Teams met twice in October in consecutive evenings in Kouvola and in February twice in succession in Vaasa. In December, HIFK and Kärpät met in the hockey outdoor show at Kaisaniemi, Helsinki.
Top six advance straight to quarter-finals, while teams between 7th and 10th positions play wild card round for the final two spots. The SM-liiga is a closed series and thus there is no relegation.