Emergency crews arrived at Duwamish Waterway Park just before 1:30 a.m. to find a man in his 20s lying on the ground with multiple stab wounds on his torso.
Attempts to revive the unresponsive young man were unsuccessful, and medics declared him dead at the scene.
It is unclear whether the victim knew his attacker.
Police canvassed the area but could not locate a suspect. Anyone with information are asked to call 911 or the Seattle Police Homicide Tip Line at (206) 233-5000. Anonymous tips are welcome.
No descriptions or other information has been made available.