an optimistic person.
a person who holds the belief or the doctrine of optimism.

Origin of optimist

1760–70; < French optimiste < Latin optim(um) (see optimum) + French -iste -ist
Related formsan·ti·op·ti·mist, noun, adjectiveo·ver·op·ti·mist, nounsu·per·op·ti·mist, noun
Can be confusedcynic optimist pessimist skeptic
Dictionary.com Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2019

Examples from the Web for optimist

Word Origin and History for optimist

1759, from French optimiste (1752); see optimism + -ist.

Online Etymology Dictionary, © 2010 Douglas Harper