Which company is older: Nestle or Hershey?

Nestle was esablished before Hershey.

Nestle was founded in 1866.
https://en.wikipedia.org/wiki/Nestl%C3%A9

Hershey was founded in 1894.
https://en.wikipedia.org/wiki/The_Hershey_Company

The Hershey Company (NYSE: HSY), until April 2005 Hershey Foods Corporation, commonly called Hershey's, is America's largest chocolate company. Its headquarters is in Hershey, Pennsylvania, a town permeated by the aroma of cocoa on some days, and home to Hershey's Chocolate World. It was founded by Milton S. Hershey in 1894 as the Hershey Chocolate Company, a subsidiary of his Lancaster Caramel Company. Hershey's candies are sold worldwide.

https://en.wikipedia.org/wiki/The_Hershey_Company

In the mid-1860s Nestlé, a trained pharmacist, began experimenting with various combinations of cow's milk, wheat flour and sugar in an attempt to develop an alternative source of infant nutrition for mothers who were unable to breast feed. His ultimate goal was to help combat the problem of infant mortality due to malnutrition.

So I would say Nestle.

I think it is Nestle

Nestlé was established first.

Hershey's was founded February 9, 1894 in Hershey, PA.
Nestlé was founded in 1866 in Vevey, Switzerland.