Rihanna's Ex-Accountants -- She Screwed Herself Out of Millions!

Rihanna's ex-accountants just fired back at the R&B singer's lawsuit against them, claiming the MILLIONS RiRi says she lost was her own fault and they had SQUAT to do with it.

If you recall ... RiRi sued her former accounting firm -- Berdon LLP -- claiming they mismanaged her dough and failed to inform her that her 2009 "Last Girl on Earth" tour was losing cash.

The singer also alleged, the accounting firm took an above standard commission from her ... at a whopping 22%.

In legal docs ... Berdon strikes back, claiming any accusations of shoddy accounting and money mismanagement are BS ... they add that the commission they took was signed off on by RiRi in an engagement letter that gave them permission to do so.

The accountants are adamant ... it was RiRi's "own financial action or inaction" or the actions of others working for her that caused her to lose MILLIONS ... not them.