Octagon Soap is a lye soap intended primarily for laundry purposes, but often used as an all-purpose soap. When used as a laundry soap, soap shavings are usually added to the water in a wash tub and laundry is hand washed using a corrugated washboard. Another way of using soaps of this kind is to put a whole soap bar in a water-filled tub containing the items to be washed. Heated from below by a fire, the contents of the tub would be stirred with a paddle. Until the 1940's, this was a common way of washing bedclothes which people wanted white and spotfree. But Octogon soap is mild enough to be used as a hand soap if one is not very concerned about skin softness.

Octagon soap was first sold early in the 1900's. During its most popular period, in the 1930's, it was a brown, roughly-cut, extruded bar of soap with coupons printed on the wrappers which could be collected and exchanged for various kinds of merchandise. A coupon can be partly seen on the lower part of the wrapper in the picture on the left.

Until 1928 Octagon Soap was manufactured by the Colgate Company. Colgate & Company was started in 1806 by William Colgate when he opened up a starch, soap, and candle business on Dutch Street in New York City. Colgate & Company became the first great soap making concern in the United States. The first Colgate advertisement (for "Soap, Mould & Dipt Candles") appeared in a New York newspaper in 1817. It was not until the 1830's that the company began selling individual bars in uniform weights.

Colgate introduced perfumed soap and began the manufacture of perfumes and essences during 1866. In 1872 Colgate began to produce the first milled perfumed toilet soap, Cashmere Bouquet. In this same year the Peet Brothers (William, Robert and James) started a soap company in Kansas City, Kansas.

In 1898, in the western United States, the B. J. Johnson Soap Company began to make a soap entirely of palm and olive oil. The advertised advantage of this soap was that it floated. The soap was popular enough that in 1916 the Johnson brothers renamed their company after it - Palmolive. In 1926 the Peet Brothers' soap company merged with Palmolive to become Palmolive-Peet. In 1928, Palmolive-Peet merged with the Colgate Company to create the Colgate-Palmolive-Peet Company. For many years after 1928 Octagon Soap was produced by Colgate-Palmolive-Peet.

In 1953 Peet was dropped from the company's title, resulting in the company's present name, Colgate-Palmolive. Octagon soap was still in limited production at the time of this writing in 1999.