The giant 21-year-old lock will start his first international against Romania at Cardiff's Millennium Stadium this Friday night alongside Llewellyn who will win his 91st cap.
And Charteris says his partners experience is already rubbing off.
'Gareth has been a great help. He was someone I watched on TV as a kid and it's great to actually be working alongside him every day, he's already been teaching me a lot,' said Charteris. 'I was reasonably pleased with how things went when I came on against South Africa but to start is a huge honour.
'I have had European experience with Newport Gwent Dragons but this is going to be a huge challenge. It's perhaps a bit earlier than I expected but once I was in the squad, my main goal was to get into the team.'
Charteris and Llewellyn are among six new faces to the Wales team that lost so narrowly to the Springboks last weekend with Cardiff Blues trio Rhys Williams, Tom Shanklin, Gethin Jenkins and Mefin Davies all in.