Andy Murray in Rio
Image credit: AFP
Murray, champion from London 2012, will face Juan Martin Del Potro in the final on Sunday as he seeks to become the first man to defend an Olympic tennis title.
Nishikori was comprehensively outclassed in the opening set and mustered just a solitary game, but made Murray work considerably harder in the second.
Just a single break of serve separated the pair in the second set as Murray held on to secure his place in another Olympic final.
Del Potro held his nerve in a final set tie-break to oust Rafa Nadal 5-7 6-4 7-6(5) in a thrilling encounter later on Saturday, with the fans creating a raucous atmosphere.
Juan Martin Del Potro - JO RIO 2016
Nadal was bidding to become the first player since 1924 to triumph in both the men's singles and doubles at a single Games, after he claimed a gold medal for Spain with partner Marc Lopez on Friday.
However, the former world number one can still depart Rio with an individual medal, should he triumph against Nishikori in their bronze medal match.
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