In her letter, Iris Frost highlighted the town's friendliness, floral displays and cleanliness.
Staying for two nights at The Camberley Hotel, on King's Road, she praised the 'perfect service and breakfast, saying she will return.
She finished her letter by writing: "I could go on and on. Everybody is so welcoming everywhere we went. I have never written before, but just had to, to lovely Harrogate."
Harrogate District Chamber of Commerce Chief Executive David Simister said: "This is a fantastic testament to what a special town Harrogate is.
"Sometimes, I think those who live and work here forget that Harrogate is the jewel in Yorkshire's Crown, and there are a great many individuals and organisations who work so hard keeping it looking at its best, whatever time of the year.
"I'd like to thank Mrs Frost for taking the time and effort to write to us, and hope that when she visits Harrogate again, we can put on an equally impressive performance."
Below is Mrs Frost's letter in full:
To all concerned
My friend and I came to stay in Harrogate for two nights and I felt I had to write to you all.
What a wonderful place I have never seen so many beautiful hanging baskets all the same outside shops on the road could go on forever. Whoever designed them all and the same flowers wow. Also, how clean everywhere no litter I think the fairies must come down when we are all in bed.
We stayed at the Camberley for us perfect service breakfast will go back.
I could go on and on everybody is so welcoming everywhere we went. I have never written to anybody before but just had to to lovely Harrogate.
Mrs Frost I am 78