Kramer, the first man to win three golds in the same speed skating event at the Winter Games, set an Olympic record of six minutes 09.76 seconds, finishing ahead of Canada's Ted-Jan Bloemen with Norway's Sverre Lunde Pedersen claiming bronze.
The 31-year-old, who won silver in the 5,000m at the Games in Turin in 2006 as well as gold in Vancouver and Sochi, started well and settled into a steady rhythm as he glided to victory in Gangneung.
Experience made the difference for Kramer, who started in the second-last pair of the evening and adapted his strategy based on how the other skaters were faring.
"To be honest I changed my strategy a bit because I saw everybody blowing up their legs," he said, pointing out how he had noticed his rivals, including Bloemen, slowing down in the final laps.
"I started a bit slower... but I really could continue. That brought me a lot in the end. Halfway during the race I was one second slower but I could bring it down to two laps in a positive way."
Kramer is the second male speed skater to win four Olympic medals in a single event, following in the footsteps of compatriot Bob de Jong, who got four medals in the men's 10,000m.
Bloemen, the world record holder in both the 5,000m and 10,000m, edged out Pedersen for silver in a dramatic photo finish.
Dutch-born Bloemen, who is eligible to race for Canada through his father, switched allegiance in 2014 and is only the second Canadian to win an Olympic medal in the 5,000m, after William Logan won bronze in the event in 1932 Olympics at Lake Placid.
"It wasn't the perfect race where you get into a flow and just fly to the finish," he said. "It doesn't always happen and it didn't happen today but I made the most out of it and I got everything out of myself that I had.
"I'm a little bit disappointed that I didn't have more to give today but overall I'm really happy and really proud to be on the podium."
Kramer and Bloemen will face each other again in the men's 10,000m on Thursday in what promises to be a fascinating battle.
(Editing by Peter Rutherford and Clare Fallon)
