Veteran forward Ronaldo returned to United from Juventus on a two-year deal, with the Red Devils retaining an option to extend that by a further 12 months.
Despite scoring 18 Premier League goals in 30 top-flight appearances this term there have been rumblings Ronaldo could cut short his return at the end of a hugely underwhelming season for the club.
United is sixth heading into its final game of the campaign against Crystal Palace on Monday (AEST), with defeat giving West Ham the chance to leapfrog them in the standings.
But Ten Hag, speaking to Dutch publication De Telegraaf, stated in no uncertain terms he is excited by the prospect of working with one of the all-time greats.
"I am looking forward to working with him," said Ten Hag. “Ronaldo is a giant, because of what he has already shown, and I think he is still very ambitious.
"Of course I want to keep him in. He has been very important for Manchester United this year and can show great statistics."
Ten Hag has won three Eredivisie titles at Ajax and the KNVB Cup twice, as well as leading the team to the Champions League semi-finals in the 2018-19 season.
That success is something United fans will be desperate for him to emulate in Manchester, with the club's last trophy arriving in 2017.
One thing Ten Hag will have to cope with is the level of scrutiny in the UK media from former United players, with the likes of Gary Neville and Rio Ferdinand particularly prominent.
"That has an impact, but it should never have an influence in the dressing room," Ten Hag added about outside opinions from former players.
"Maybe the criticism is fiercer there. The club simply has a bigger fanbase and more reach than Ajax, because England is much bigger, the Premier League is much bigger and basically everything is much bigger.
"Compared to the Netherlands it's factor two, three, four or maybe even more. Fortunately, I've been getting more and more baggage on how to deal with certain forces."
Ten Hag also stated that he will begin work with United from Monday.
"We have agreed that I will be employed by Manchester United from 16 May," he said. "In the preparation for the season there are still a few things to be done.
"Among other things, regarding the filling of the staff and the composition of the selection. I will make my mark and that must be done extremely carefully.
"We have to talk carefully about where we all want to go and how we are going to achieve that. There were possibilities to work at clubs where it is easier, because there is a better foundation.
"But I chose United because there's something to be gained there. A lot of things need to be addressed and that's a challenge. The club and I are on the same page as far as that's concerned.
"Also about the way I want to do it. In what way? I don't want to say anything about that. I will discuss that in England."