A wedding breakfast is a dinner

Dinner

Dinner is usually the name of the main meal of the day. Depending upon culture, dinner may be the second, third or fourth meal of the day. Originally, though, it referred to the first meal of the day, eaten around noon, and is still occasionally used for a noontime meal, if it is a large or main...

 given to the bride

Bride

A bride is a woman about to be married or newlywed.The word may come from the Proto-Germanic verb root *brū-, meaning 'to cook, brew, or make a broth' which was the role of the daughter-in-law in primitive families...

, bridegroom and guests at the wedding reception

Wedding reception

A wedding reception is a party held after the completion of a marriage ceremony. It is held usually as hospitality for those who have attended the wedding, hence the name reception: the couple receives society, in the form of family and friends, for the first time as a married couple. Hosts...

 that follows a wedding

Wedding

A wedding is the ceremony in which two people are united in marriage or a similar institution. Wedding traditions and customs vary greatly between cultures, ethnic groups, religions, countries, and social classes...

 in the United Kingdom

United Kingdom

The United Kingdom of Great Britain and Northern IrelandIn the United Kingdom and Dependencies, other languages have been officially recognised as legitimate autochthonous languages under the European Charter for Regional or Minority Languages...

, Germany, Austria, Scandinavia and some other English-speaking countries. The Compact Oxford Dictionary lists the phrase as only “British”, and the Merriam-Webster online dictionary does not list it at all.

The wedding breakfast is not normally a morning meal, so its name is puzzling. The name is claimed to have arisen from the fact that in pre-Reformation times the wedding service was a Mass and the bride and bridegroom would therefore have been fasting

Fasting

Fasting is primarily the act of willingly abstaining from some or all food, drink, or both, for a period of time. An absolute fast is normally defined as abstinence from all food and liquid for a defined period, usually a single day , or several days. Other fasts may be only partially restrictive,...

 before the wedding; after the ceremony the priest would bless and distribute some wine, cakes, and sweetmeats, which were then handed round to the company. Since in the old Catholic custom no-one may take Mass unless they have fasted since daybreak, this was literally a “break fast” for the bride and groom, though others in attendance would not necessarily take communion and therefore would not necessarily have been fasting. The author of Party-giving on Every Scale (London, n.d. [1880]) reported a more direct origin:

The orthodox "Wedding Breakfast" might more properly be termed a "Wedding Luncheon," as it assumes the character of that meal to a great extent; in any case it bears little relation to the breakfast of that day, although the title of breakfast is still applied to it, out of compliment to tradition. As recently as fifty years ago luncheon

Luncheon

Luncheon, commonly abbreviated to lunch, is a mid-day meal, and is smaller than dinner.In English-speaking countries during the eighteenth century, lunch was originally called "dinner"— a word still used regularly to mean a noontime meal in Scotland, Ireland, Wales and some parts of England,...

 was not a recognized meal, even in the wealthiest families, and the marriage feast was modernized into the wedding breakfast, which appellation this entertainment still bears.

The Oxford English Dictionary

Oxford English Dictionary

The Oxford English Dictionary , published by the Oxford University Press, is the self-styled premier dictionary of the English language. Two fully bound print editions of the OED have been published under its current name, in 1928 and 1989. The first edition was published in twelve volumes , and...

does not record any occurrences of the phrase "wedding breakfast" before 1850, but Queen Mary

Mary I of England

Mary I was queen regnant of England and Ireland from July 1553 until her death.She was the only surviving child born of the ill-fated marriage of Henry VIII and his first wife Catherine of Aragon. Her younger half-brother, Edward VI, succeeded Henry in 1547...

 and Philip of Spain

Philip II of Spain

Philip II was King of Spain, Portugal, Naples, Sicily, and, while married to Mary I, King of England and Ireland. He was lord of the Seventeen Provinces from 1556 until 1581, holding various titles for the individual territories such as duke or count....

 are known to have had their wedding breakfast at the East Hall of Wolvesey Castle on 25 July, 1554. So this custom, like the Christmas tree, may have been popularized in Britain or reimported from Germany during the Victorian period, because of Queen Victoria's German husband, Prince Albert.