Leicester Tigers scrum-half Ellis was among the 37-man squad announced on Tuesday.
Ellis, who has 27 England caps, said: “I was out training when I heard. It is an honour to be involved and a privilege to be in the squad.
“One of the lads told me on the training park. I was shocked. I didn’t really believe it.
“I got back in (from training) and read it. It is brilliant, a massive honour and something as a player that you want to do. I am very lucky that I am in among some great players.”
He added: “I didn’t really think about it as a youngster because I didn’t think it would be attainable, to be honest.
“My dream was always to play for Leicester and I didn’t really think about anything else. As I said, it is a great honour and I am very pleased.”
It will be the second time Ellis has toured South Africa after playing there when he was a pupil at Leicester Grammar School.
Ellis said: "“I have toured there for my school, Leicester Grammar. We toured there in 1999. I have some good memories from then.
“It is a great country. I am looking forward to the prospect of being involved and getting some game-time out there.”
He added: “I am really looking forward to it but now I am concentrating on this game this weekend. We have a massive game for Leicester this weekend against Bristol, so I am preparing for that.”
Tigers take on Bristol Rugby at the Walkers Stadium in their last game of the Guinness Premiership regular season where a win would guarantee a home play-off semi-final.
Ellis said: “There is a lot of hard work to come in the next few weeks. We have been training really hard and we need to perform as well as we can to get a victory against Bristol.
“They are a great team and we need to concentrate on what we need to do to get a victory for a Guinness Premiership semi-final.
“A home semi-final does help. The crowd this year at Welford Road have been amazing and the quarter-final at the Walkers Stadium, they were immense. They always are. That’s why it is so great playing for Leicester, the fans are outstanding and hopefully they will turn up again this weekend in their numbers.”
Tickets for Saturday’s game against Bristol Rugby at the Walkers Stadium are available on 0844 856 1880, online or by calling in person to the Tigers ticket office.