Guenther, an Edmonton native, had 103 points (56 goals, 47 assists) in 30 games with the Northern Alberta Xtreme bantam prep team.
The Oil Kings, who finished the 2017-18 WHL season in last place with a 22-42-8 record, won the first overall pick in the WHL draft lottery.
The Kootenay Ice picked defenceman Carson Lambos second overall. The Winnipeg native had 40 points in 30 games with the Rink Hockey Academy Nationals.
Defenceman Nolan Allan went third to the Prince Albert Raiders, while Sean Tschigerl (Calgary Hitmen) and forward Logan Stankoven (Kamloops Blazers) rounded out the top five.
Fourteen forwards and seven defencemen were among the 22 players selected in the first round.
Tyler Brennan was the only goaltender taken in the opening round after being selected 21st overall by the Prince George Cougars.