What is this white growth on my female dog?

Can you tell me please what this white growth is on my female dog?

Hello!  Out of context, it is difficult to tell where abouts on the dog we are. Is this the vulval fold, tail fold, ear or something else?

In any case, it could be a viral lesion, a papilloma or wart, or thickening brought about by friction at that crease.  Moreover, I can't rule out more sinister options eg tumours.   It would be a good idea for your vet to examine this in context.  Some warts fall off / disappear so they will have a decision to make as to whether they want to wait and see,or identify the lesion as soon as possible.  This is a decision best made in context.