"We didn't do enough to get to the final," Mbappe told reporters. "They (Spain) played better than us, they deserved to go to the final and we are going home."
Mbappe set up Randal Kolo Muani's ninth-minute opener, but Spain hit back to take the lead with two strikes in four minutes midway through the first half.
"I had the ambition of becoming European champion. I had the goal of having a good Euros. I did neither. It's a disappointment," said Mbappe.
France scored just four goals in the tournament, with Mbappe's only strike coming from the penalty spot.
The haul was in stark contrast to France's run to the World Cup final in Qatar, where Mbappe scored eight of Les Bleus' 16 goals.
Mbappe had a late chance to level the scores when he cut inside from the left flank with just goalkeeper Unai Simon to beat, but blasted over the bar.
"I got past the defender and it went well. Afterwards, I thought I just have to score or at the very least get it on target.
"It went over the bar. That's the harsh reality of football. 2-1 and we're going home."
The France captain had played in a protective mask after breaking his nose in the opening match against Austria, but removed it for the semi-final, saying he was "fed up".
"I couldn't see well with it. I spoke to the doctor to see if I could play without it.
"He told me to make the decision like a man. And there you go, I played without it and I don't regret it."
