Rita Ora is to perform in front of Pope Francis at the Vatican this weekend ahead of Mother Teresa's canonisation.
The British-Kosovan singer and TV star, 25, said her upcoming gig is "massive" and that it is a "real honour" to perform in front of the leader of the Catholic Church.
Ora spoke candidly during an appearance on US chat show The Tonight Show, admitting that she is "a spiritual person" and that "the Vatican is actually a big deal".
The show's host Jimmy Fallon agreed, to which she replied: "Then I looked at the guest list and I see the Pope! I thought, what do you wear to see the Pope?"
Ora revealed she will be singing traditional Christmas song What Child Is This.
She said: "It's massive, I'm really looking forward to it. It's actually to celebrate Mother Teresa, who has now become a saint.
"It's a real honour, and I don't know if anyone's really done the whole Vatican venue thing before."
She added: "It's a bit interesting that the Vatican is someone's venue. It's going to be fantastic."
Mother Teresa, who was also born in Kosovo, is to have her sanctity as a saint sealed by Pope Francis during a canonisation Mass in St Peter's Square on Sunday, the eve of the 19th anniversary of her death.
Pope Francis set the canonisation date, paving the way for the nun who cared for the poorest of the poor to become the centrepiece of his year-long focus on the Catholic Church's merciful side.
The announcement was expected after Francis in December approved a second miracle attributed to Mother Teresa's intercession - the final hurdle to make her a saint.
The Vatican ceremony is expected to draw tens of thousands to honour the nun who was fast-tracked for sainthood just a year after she died in 1997. St John Paul II, who was Mother Teresa's greatest champion, beatified her before a crowd of 300,000 in St Peter's Square in 2003.
Ora is best known for her work as a musician and has also appeared as a judge on TV talent programmes The Voice UK and The X Factor.
Her first album, Ora, was released in 2012 and debuted at number one in the UK, and she is yet to release her second record.