Gareth Bale came off the bench to score Real Madrid's winning goal with his first touch in their Fifa Club World Cup semi-final against Al Jazira.
Bale, 28, scored moments after coming on for only his second appearance since suffering a calf injury in September.
Al Jazira had taken a first-half lead through Brazilian forward Romarinho.
Mbark Boussoufa then had a strike ruled out for offside by the virtual assistant referee before Cristiano Ronaldo equalised for Madrid.
The Portuguese is now the all-time top scorer in Fifa Club World Cups with six - taking him past Lionel Messi, Luis Suarez and Cesar Delgado's five.
The Club World Cup features Fifa's six reigning confederation champions plus the league winners, Al Jazira, of the host country, United Arab Emirates.
Zinedine Zidane's side will now play Brazilian side Gremio in Saturday's final.
Joy Sports Gary Al-Smith was at the Zayed Sports City Stadium to see Los Blancos win, and filed this instant spot-report.
Zidane also defended Benzema, and promised not to sell the striker, as Al-Smith narrates here.