The preview, beginning at 12.15pm, will also see the launch of Rhinos’ 2019 home shirt.
The kit celebrates the 20th anniversary of their record Challenge Cup win over London Broncos in the final rugby league game at the old Wembley Stadium.
The South Stand, replacing the previous all-standing structure which dated from the 1930s, will be officially opened when Rhinos take on Wakefield Trinity in the Wetherby Whaler festive Challenge on Boxing Day.
Demolition work on the former South Stand began in August last year.
Some of the new standing terrace was opened during this year’s Betfred Super League season and seats have been in use for the past two Yorkshire Carnegie rugby union fixtures, but today’s event will allow fans access to the changing rooms and dugouts as well as matchday facilities.
Rhinos chief executive Gary Hetherington described the new stand – part of the stadium’s £40m rebuild – as “phenomenal”.
He said: “It is everything we would have hoped for in terms of what has been delivered.
“The terrace capacity is almost what we had before, everybody who stood in the old South Stand will be able to do the same again.
“We have a really plush seating terrace and all the facilities – toilets, bars and food outlets – are going to be that much better.
“The turnstiles are on the perimetre so once you are into the car park you are in the stadium.
“Everything about it is first class.”
The open day will give fans an opportunity to try out the seats and standing areas and the concourse, including bars and catering, will be open.
There will be a junior rugby festival on the pitch and the first Test between England and New Zealand, which kicks off at 2.30pm, will be shown live on the stand’s video walls.
Though many of Rhinos’ squad are on holiday or representative duty, some players will be present including Brett Ferres who will preview the Test match and give his thoughts after the game.
Hetherington added: “We want people to give us their opinions.
“Even though it [the South Stand] is open and handed over, it is not yet finished.
“There will be other features, we will be fitting a lot of history and heritage into the South Stand.
“There’s still quite a bit to be added to it, but it will be interesting for people to come and get a feel for it.
“I will be giving an update on the rest of the stadium development and doing a question and answer session on where we are with the rest of the stadium.”
The temporary stand on the cricket side of the ground, used last season, has been removed. The new North Stand, shared with Yorkshire County Cricket Club, is due to officially open in May.