Ronaldo reacted angrily to being dismissed during the second half of a 3-1 first-leg Supercopa victory for Real against Barcelona in last Monday.
The 32-year-old, who came off the bench, scored the third goal of the visitors at Camp Nou but earned a second yellow card for going to ground in the penalty area two minutes later, having earlier been booked for taking his shirt off in celebration.
Following which, he was handed a five-match ban, a decision that was upheld by Spain's Administrative Court of Sport (TAS) on Tuesday.
"One more incomprehensible decision. From injustice to injustice, they will never overthrow me," goal.com quoted Ronaldo as saying on Instagram.
"And as always I will come back stronger. Thank you to all who have supported me," he added.
Real won the Supercopa 5-1 on aggregate against Barcelona and opened their league season with a 3-0 win at Deportivo La Coruna in Ronaldo's absence on Saturday.
The Portuguese will not return to domestic action until September 20 against Real Betis, but can play in the Champions League.
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