If it's a true gift, you do not have to pay tax on it, or even report it on your tax return.
Your parents would have to file a gift tax return. They will not have to pay any gift tax unless the lifetime total of gifts they have given is more than $11,580,000, but they have to file the return. The gift will reduce their lifetime gift and estate tax exclusion.
Before making a gift of that size, you and your parents should consult both an estate lawyer and a tax professional who specializes in high-net-worth individuals.
If there are any restrictions or understandings about what you will do with the money, or if you are expected to do something in return, then it is not a true gift and other considerations might apply, and it could be taxable income to you. Again, you need to consult a lawyer and a tax professional.
