In promotion and of advertising, a testimonial or endorsement consists of a written or spoken statement, sometimes from a public figure, sometimes from a private citizen, extolling the virtue of some product. The term "testimonial" most commonly applies to the sales-pitches attributed to ordinary citizens, whereas "endorsement" usually applies to pitches by celebrities. See also Testify, Testimony, for historical context and etymology.

Written testimonials in the history of advertising

Testimonials are in the form of letters and ad copy featured very commonly in the advertising of patent medicines in the 19th and 20th centuries. The pages of almanacs and other promotional literature filled up with multiple testimonials,some with accompanying photographs, that tell of the healing powers of the products in question. Dr. R. V. Pierce, marketer of Pierce's Golden Medical Discovery, published The People's Common Sense Medical Adviser in 1875; its publication continued for forty years. In addition to a fair explanation of medical knowledge at the time it appeared, this book contained literally hundreds of testimonials extolling Pierce's nostrums, or talking up the virtues of Pierce's Buffalo, New York clinic. Stern photographs of women who owe the cure of their "female weakness" to Pierce's medicines accompany many of the letters. A Denver, Colorado man's testimonial affirms that they put an end to his self-abuse:

Case 461,306. Onanism. Melancholia; contemplated suicide.

Gentlemen — Having waited several weeks after finishing the last medicine, to see if there would be any relapse, I now send you a report of treatment. I believe I am thoroughly cured, not only of poor health, but of all desire to abuse myself. I have regained health, spirits, and confidence. Am married, something I have long desired, but never before dared to attempt. Please accept my sincere thanks, gentlemen. Your medicine has saved me from a suicide's grave.

--- H., Denver, Col.

Not only anonymous persons, but occasionally politicians, entertainers, and other celebrities offered their endorsements to the vendors of patent medicine. The makers of Vin Mariani, a cocaine-laced patent medicine, secured one of the most valuable testimonials ever by receiving the recommendation of Pope Leo XIII. Queen Victoria also endorsed a number of patent medicines and other products, and the frequently-seen notices touting a manufacturer or a product "by appointment to" a monarch or his family continue the practice of royal endorsement in a somewhat more low-key manner.

Such coups came towards the end of the era of written testimonials. Later advertisers found that no one bothered to read the testimonials anymore; the sheer bulk of their numbers made them no more convincing or appealing. A warier public wondered whether these anecdotes really proved anything, and often doubted their genuineness.