Gift My Mom $100,000 - Will I Have To Pay Gift Tax?
You will not have to actually pay gift tax, but you will need to file a gift tax return (Form 709). "Gift tax" is a bit of a misnomer as most people aren't actually paying the gift tax. What you are doing is reporting that you made gifts over the annual exclusion amount and then you have to reduce your lifetime exemption amount by this amount. Since you said you haven't made any previous gifts, you will have your full exclusion amount to use before you would have to worry about the actual gift tax (its $5.49 million as of 2017 and is scheduled to double next year due to tax reform).
Here is a really good overview of the gift tax and towards the bottom are some more specific examples and advice on filing Form 709.