The Norwegian mastered relentless conditions which included compacted snow and polished ice to win Saturday’s opening pair of stages in his Skoda Fabia Rally2.
A steady drive on the second pass of La Bréole - Selonnet saw him end the day 2min 13.8sec out in front. Mikkelsen was pleased with his performance and thanked his ice crew for their support throughout the day.
"We have a big lead and we have to take care of it as well as possible. For us, it's quite easy now - we don't need to push and we just have to get to the end," he said.
M-Sport Ford Fiesta Rally2 pilot Adrien Fourmaux held onto second place, although his Saturday wasn’t without drama. A puncture during SS10 cost the Frenchman one minute and put him under pressure from Eric Camilli’s Citroën C3.
A win on the final stage of the day allowed Fourmaux to put some breathing space between him and his rival and the advantage was increased to 17.6sec.
Marco Bulacia trailed his leading Skoda team-mate by 8min 28.3sec in fourth after a slippery day on the stages, whilst Sean Johnston ended another 3min 1.0sec behind in his C3.
Skoda man Enrico Brazzoli completed the leaderboard 39min 28.6sec off the leading pace in sixth.
• Full coverage from Rallye Monte-Carlo will be available on WRC+ All Live here, including every stage broadcast as it happens as well as key interviews, features and expert analysis from the service park.