Or do you have to provide your own?
That;s going to depend on the company. While it's by no means unheard of it's not what a typical office manager at a typical (non-creative type office) would see as a normal computer peripheral, so you may have to make a case for having your office purchase it.
If you're working at a very graphics-intensive shop, however, it probably would be considered standard equipment for a designer.
I work at a graphics intensive design agency.
Unfortunately, design tablets are not seen as essential hardware. Nobody here uses them, but I'm sure if I made the case that my speed and efficiency would improve with one, then a purchase may be made.
It depends entirely on the agency, but at the same time it depends entirely on the user.
Just add to @Daniel Hanly's and @lawndartcatcher's excellent answers... If you are considering bringing in your own, you will want to check with your company's IT department, or whomever holds responsibility for computer integrity, because plugging in your own kit may be a violation of company policy.
Assuming you're a long-term worker on company premises, you should make a case that it's required in order to achieve an outcome beneficial to them (precision, efficiency, ability to deliver new kinds of artwork).
Then they can either accept it's required, and that they should buy it for you, or reject it and accept the status quo.
I don't think there's ever a good case for bringing your own in.
I think it really depends upon the company.
If a company is one which stays on top of current software versions, rather than working with 4 to 6 year old versions. That's a good sign.
If a company encourages designer training or training reimbursement, that's a good sign.
I've worked for companies with follow these general mindsets and for companies which would never. I've honestly never had an issue requesting a Wacom tablet when equipment is being upgraded or when I was hired if the company was proactive rather than just letting things run until the wheels fell off.
For an entry level position... it may be difficult unless there are more senior designers/directors already using tablets or at least already understand the benefits.
In any event, I would strongly suggest you do not bring in your own tablet. There's all sorts of legal stuff which could arise from you supplying hardware or tools to a work-for-hire position (fulltime/part time employment). Its unlikely anything would come of it, but if the company were litigious should you have a falling out, it could end up being more trouble than it's worth.
edit: erm... oh.. just saw the date on this.... Probably no point in my response :)