Djoker was a heavy favorite against the 27-year-old Russian qualifier, who was making his debut in the main draw of a Grand Slam, and the world No. 1 dominated from the start, needing only one hour and 53 minutes to move on.
The victory gave Djokovic the ninth Australian Open final berth of his career, and he will now await the winner of the second semifinal between No. 4 Daniil Medvedev and No. 5 Stefanos Tsitsipas.
Karatsev was playing with house money Thursday, but it was difficult to imagine him beating a player who had never lost in eight previous trips to the Aussie Open semis.
He battled to beat the likes of Diego Schwartzman, Felix Auger Aliassime and Grigor Dimitrov en route to the semifinals, but Karatsev was overmatched against arguably the greatest player of all time.
Djokovic dominated the match in essentially all areas, especially when it came to the serve:
Djokovic broke Karatsev six times in seven chances, while Karatsev converted two of his five break-point opportunities, which wasn't nearly enough to pull off the upset.
He also committed 30 unforced errors to just 14 for Djokovic, and that clean play was a huge contributing factor in Nole's triumph.
While it wasn't the result Karatsev wanted, he was showered with affection by the fans in attendance after the match:
Given Djokovic's dominance in Melbourne over the years, he was the overwhelming favorite to win it all entering the tournament, and that remains the case after his virtuoso performance Thursday.
Djokovic is the two-time reigning Australian Open champion, and he has won the tournament eight times during his career overall.
Djoker has never lost in an Aussie Open final, and he said Thursday that his clean sheet in the final is an immense help to his confidence level:
While many were anticipating or hoping for a Djokovic vs. Rafael Nadal final, that won't be the case after Rafa was knocked out in the quarters in a five-set classic against Tsitsipas on Wednesday.
Djokovic will instead have to face one of the top young guns in tennis in either Medvedev or Tsitsipas, both of whom are looking for their first Grand Slam title.
Djoker is just 4-3 against Medvedev, losing three of their past four meetings, and he is 4-2 against Tsitsipas but is on a three-match winning streak against the Greece native.
The expectation is that Djokovic will win regardless of his opponent, but given the fact that he hasn't dominated either of his potential opponents, a ninth Aussie Open title is far from guaranteed.