The midfielder has been a revelation at Dortmund since joining for 20 million euros ($22.8m) from Chinese side Tianjin Quanjian after his impressive performances at the World Cup helped Belgium finish third.
Witsel is relishing his first appearance in 'Der Klassiker', with third-placed Munich trailing Dortmund by four points.
"Yes, I am a leader," Witsel, who turns 30 in January, told reporters on Thursday.
The Dortmund team is packed with rising stars like 18-year-old England winger Jadon Sancho, full-back Achraf Hakimi and US winger Christian Pulisic, both 20, and Witsel enjoys having to keep up with players a decade his junior.
"We have a group that is really young, with players from 18 to 25 years old, so it's up to us 'oldies' to guide them in the good times and also when things don't go so well," added Witsel.
Witsel has not just been Dortmund's midfield enforcer as he often is for his national team.
He has weighed in with three goals, including the winner in the German Cup first round at Greuther Fuerth and the first in Dortmund's 4-0 thumping of Atletico Madrid in the Champions League two weeks ago, before they lost the return match 2-0 away on Tuesday.
"(Coach Lucien Favre) deserves a lot of credit for the game we are playing at the moment," said Witsel.
"I do not have the same role as in the national team, where I have to stay back and control things.
"I like both roles. In the national team I feel great, but here it's a lot of fun to push forward from time to time.
"But I'm not a 10 (behind the striker), I'm still an 'eight', a box-to-box player."
No title talk
Dortmund are the only team yet to lose in Germany's top flight this year and with Bayern third after defeats to Hertha Berlin and Borussia Moenchengladbach, Witsel sees a great chance for the hosts.
"They have not been good for a few weeks, so it's up to us to take advantage," said Witsel.
"But it's not going to be an easy match. Bayern can wake up for games like this, so it will be up to us to pay attention."
With two thirds of the season still to go, Witsel says no one in the Dortmund squad is yet daring to dream of a first league title since 2012 despite their unbeaten start.
"The goal is to qualify for the Champions League next year, so we are in a favourable position, but no-one in the dressing is talking about winning the championship," he insisted.
A crowd of over 80,000 is expected and Witsel is looking forward to playing Dortmund's biggest league home game of the season in front of Signal Iduna Park's famous 'Yellow Wall' -- the south stand which holds almost 25,000 baying fans.
"This is my first (home game against Bayern) and I can't wait to see how it feels in terms of atmosphere," Witsel said on Thursday.
"Although every time we play at home there is a mad atmosphere, I think against Bayern it will be a little more."