Ray Lewis was previously seen as the voice of the team, but the linebacker retired following the AFC North side's Super Bowl win in February.
The 28-year-old told the team's website: "I am the leader. Whether you believe that or not plays into what you think my personality is. I think I'm born to be a leader. I think that's why I play quarterback. I think that's why we have a good team.
"My first job was to come in here and prove to everybody that I could play. I didn't want to come in here and act like a big shot."
Linebacker Terrell Suggs added: "I would say it's Joe. A lot of us have been here, and out of eleven years, I didn't get a ring until he got here. So I'll say it's him."
The Ravens have reached the playoffs every year since drafting Flacco in 2008.