Sisu is a Finnish male first name. While it was relatively rare at the end of the 20th century, it has become more common in the 21st century. By the end of 2019, the name had been given to approximately 2,550 individuals, with nearly 99% of them born after the year 2000. Since 2015, Sisu’s name day has been celebrated on February 28th, which is also the day of Kalevala, and was already the name day for Onni.