As nearly as historians can pin it down, the engagement ring began as a betrothal or "truth" ring in ancient Rome. The tradition of wearing it on the third finger of the left hand also began in Rome, whose congress with Egypt convinced them that the vein of that particular finger led directly to the heart. The Romans were also the first to begin inscribing and engraving their rings, especially engagement rings. Diamonds were in use even in those early days, prized for their supernatural abilities to guard the wearer from poison, insanity and fears.

The Middle Ages, from 500 A.D. to around 1500 A.D. saw developments for bridal jewelry. The rings were known Gimmal or "bond" rings and set with sapphires, rubies and emeralds for those who could afford them. The richest suitors gave diamond bond rings for very romantic occasions. Since diamonds were known as the strongest material, resistant to both fire and steel they symbolized an unbreakable love.

In 1215, Pope Innocent III enacted a longer waiting period between engagement and marriage, which led most lovers to present their bride to be with a plain gold, silver or iron ring. The aristocracy began to [ornate their rings with gems|add gems] in order to distinguish themselves from the "common folk" and indeed, laws were even passed to prevent anyone but the wealthy from wearing precious stones. The laws eventually relaxed enough to allow the middle classes to wear jewels if they could afford them. Six-stone engagement rings were common then, containing the birthstones of the bride and groom in the center, flanked by the birthstones of their parents. Many of these rings also had compartments to accommodate a treasured lock of the suitor's hair.

In 1477, Maximilian the Archduke of Austria gave Mary of Burgundy a diamond betrothal ring, beginning the tradition of diamond engagement rings in Europe. Still, only the wealthiest families could afford them, as there were very few places from which they were mined. The Italians thought that diamonds ensured a pleasant marriage and kept a couples' love alive. This lore made the diamond even more popular near the end of the Middle Ages.

In the 18th century, more diamonds were discovered in Brazil. The supply and demand became more balanced so many more people were able to afford to give diamond rings as betrothal gifts. Cluster engagement rings were fashionable among the rich of this era. Then, in 1870, the Kimberley diamond region was discovered in South Africa and diamonds became even more affordable. As more men were able to buy their brides to be diamonds, the wealthy classes began using birthstones in betrothal rings to separate themselves from the "vulgarity" of the lower classes. Not willing to abandon diamonds altogether, however, they often used diamonds as accents to the sapphires, emeralds aquamarines and topaz that were the central stones of the rings. The Regards and Dearest rings were also presented upon betrothal, the words spelled out with gems whose names represented the letters in those words.

The diamond engagement ring really caught on, particularly in America, when the DeBeers company began a concerted campaign to boost sales that were flagging due to the financial hardships of the 1920's and 30's. The 1947 slogan "A Diamond is forever" was the first in a series of successful advertising strategies. It worked so well that, coupled with another campaign to encourage families to keep diamond jewelry as family heirlooms, the demand for the stone skyrocketed.

Today, the diamond engagement ring is here to stay. 78% of all engagement rings purchased are diamonds set in gold, silver or platinum. Other countries have adopted the tradition of engagement rings, too. In Egypt, Brazil and many European nations, the groom also receives an engagement ring and in Spain, a woman will often buy her lover an engagement watch.