The 25-year-old set a relentless pace, leading from early on to finish in warm conditions and take gold in a personal best of three hours, 38 minutes and eight seconds.
Olympic bronze medallist Aleksey Voyevodin kept tabs on his compatriot until halfway but was shaken off and had to settle for silver in 3:41:25. Italy's Alex Schwazer, seventh at the halfway stage, rallied to take bronze in 3:41:54.
Triple world and Olympic champion Korzeniowski, the greatest walker in history, retired after winning his third Games 50 km title last year.
Kirdyapkin, in his first world championships, put his rivals under pressure on a sunny bright morning in the Finnish capital, a marked contrast to the wet and windy weather that had blighted previous days of competition.
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The experienced Voyevodin, 10 years his compatriot's senior, was shoulder to shoulder with Kirdyapkin at the 20 km mark and just two seconds down at halfway.
Slowly but surely, however, Kirdyapkin burnt off his rival and with 15 km to go had opened up a commanding lead that he never relinquished.
China, boasting athletes with the three fastest times this year, failed to mount a title challenge with Zhao Chengliang finishing the best of their three walkers in fifth place.
