Toni Collette

Toni and Jonny dated after filming Velvet Goldmine in 1998

Toni later described the relationship as hedonistic, drunken and "probably dangerous". The couple stayed together for around a year, with Collette spending much time at Rhys Meyers' home in Cork, Ireland. Indeed, she'd was so enamoured with the Emerald Isle that she'd buy her own place in the Wicklow Mountains. She admitted in an interview later that she suffered from 8 months of panic attacks following their break up. She is now happily married to musician and fellow Australian Dave Galafassi.

Toni Collette recently said in an interview for the Daily Mail Weekend Magazine on the 2nd December 2006:
When in Velvet Goldmine, she fell in love with her co-star Jonathan Rhys Meyers. She looks back fondly on the relationship 'We had a wonderful time together. He is very interesting, charming, soulful person. It was just one of those relationships you have to have,' she adds mysteriously.
But it wasn't forever? 'clearly not', she says bluntly. 'But it was everything while it lasted.'

Cha Cha is an Irish Model, and at the time of dating she was a student of anthropology and came from Dublin, D4.
They got engaged in 2001.
Jonathan said this to Showbiz Ireland:
"We are madly in love and got engaged ages ago but we kept it quiet as we just like to keep things to ourselves.

17th September 2002 ShowbizIreland annouced Jonny split with his fiancée Cha Cha Seinge.
This is what Showbiz Ireland said about the split:
When we met the great Jonathan in Renards nightclub last month he told ShowBizIreland.com that himself and Cha Cha were still an item.
So we have all been waiting for the sound of wedding bells since their engagement last year.
However, last week Cha Cha confirmed the couple had been having issues and have since gone their separate ways. They remained friends and in an interview last year with the Sunday Times, he described her as "Beautiful, with eyes like a kitten and a gap in her teeth. Gorgeous, I was so besottedly in love with her." He also has said she was his first true love.

Cha Cha 1 Taken from ShowBizIreland
Cha Cha 2 Thanks to Gail from Mystic Bliss site

Lisa Butcher

Lisa is a Society Model, well known within the London Circle. She was previously married twice - the latter producing two children.
Jonathan and Lisa dated on and off for about a year after meeting at the Veuve Clicquot chateau in France, a party held to launch the lastest film remake of The Impotance of Being Earnest they rumoured to have broken up due to Jonathan's schedule.

In an Interview from the Evening Standard dared 27th January 2003, Lisa states:
They first met during "an amazing weekend" at a French chateau last summer.
Lisa had been invited by a champagne company to an Oscar Wilde dinner. She was seated next to Rhys Meyers and they immediately started talking.
That was last summer and they have been an item ever since.
"I hadn't seen any of his films, so it wasn't as though I were a fan," she says. "After we met, I got all his films out on video and he's really rather good. He's an incredibly generous and warm- hearted person. He also has this incredibly sexy Irish accent."

Thanks to Story Spice for sending me this info :D

Harry Harrison:

This was a very quick relationship and we don't think there are any pictures of them dating. She is a singer in a band called Dirty Harry who are based in London.

Asia Argento
He dated Asia Argento during the time of "B Monkey" - Asia later said of the affair: "Actors are very dull lovers. Even Johnny Rhys Meyers — we had an affair, but he was always talking about what he did in his last film, or what he was going to do in the next one. He grew up on a farm on an island, and it seems like the big dream of making it in Hollywood is f***ing him up a bit. He could be much better." (source OdetoAzia)

In the Italian Vanity Fair magazine June 26th 2006, Jonathan talked about Asia saying: "Me and asia had a small fling, seven years ago. She’s not as crazy as she wants others to believe, she is incredibly intelligent and smart. But I was too young and too weak for her. Who, instead needs a strong man"

Lady Victoria Hervey:

Another very short rumoured relationship, in which Victoria explained that they had a few dates but nothing past that

In July 2006, Lady Victoria Hervey took part in ITV1's celebrity "Love Island", where you go on the island of Fuji, with other celeb to find love.
A news story reports this: "She's been seeing Jonathan. But Victoria has been desperately trying to keep her romance very hush-hush as she doesn't want anyone to find out. They rekindled their romance after she agreed to take part in the show.

"It's really early days between them and she decided to go for it because she needed the money and the publicity as her Hollywood career never exactly took off." Victoria and the Dublin-born Mission Impossible III star previously dated in 2004. They rekindled their romance when they recently met up in Los Angeles following his split from on-off long-term girlfriend, Reena Hammer in May.

Reena Hammer -The current Girlfriend

Reena is half Bangladeshi and half Polish/English, born in England. Her dad owns a spa, at the top of Harriods in London and her mother is top make up artist and co-owner of Ruby and Milne Make Up Products - Ruby Hammer.
Reena and Jonathan started dating in 2004 and have been seeing each other for over a year now and live together in London. Recently they have been spotted at a variety of Premiere's and parties and Jonathan has said he is the "Luckiest man in the world to be with her"

In January 2005 they had a tumultuous time of it but seem to be back on track and very much in love

In May 2006 they called an end to their relationship, but by february 2007 things looked back on track for the couple and they brought a pad out in LA

Pictures taken from Getty Images.com

RUMOURS:

Rachel Leigh Cook
Apparently he dated Rachel Leigh Cook whilst film "Tangled"

Estella Warren
he has also stated he dated Estella Warren although has not confirmed if it was also during the filming of "Tangled"

Thanks to Gail from Mystic Bliss site for helping me with some information on the girlfriends :0)