Who is the leader of the Rebel Alliance in the original trilogy (commonly shown giving briefings)?

The story behind the answer

Seen in Return of the Jedi delivering the sober briefing on the strike against the second Death Star, she serves as the Rebel Alliance’s civilian leader and chief political strategist. Don’t confuse her with Princess Leia, who leads on the ground as a military commander and diplomat; Admiral Ackbar, a fleet commander who directs the Endor space battle but reports to Alliance leadership; or Bail Organa, an early architect of the Rebellion who dies with Alderaan before most original-trilogy events.

A former senator from Chandrila, she helped formalize the Alliance from disparate cells, embodying its political legitimacy and unity. Her role is expanded in Rogue One and animated series, showing how diplomacy, not just starfighters, held the Rebellion together.