The 18-year-old from Belle River, Ont., is seen as a potential franchise defenceman who is ahead of many of his fellow juniors in terms of size, strength and maturity.
Ekblad had 23 goals, 30 assists and 91 penalty minutes in 58 games last season.
The six-foot-three 216-pound blue-liner was granted exceptional player status by Hockey Canada to enter the Ontario Hockey League at age 15.
Ekblad was ranked second among draft prospects by the International Scouting Services, which had Kootenay centre Sam Reinhart No. 1. NHL's Central Scouting had him No. 2 behind Kingston centre Samuel Bennett.
The last defenceman to go first overall was Erik Johnson, who was taken by St. Louis in 2006.