Miai (見合い, "matchmaking"; literally "look meet"), or omiai (お見合い) as it is properly known in Japan with the honorific prefix o-, is a Japanese traditional custom which relates closely to Western matchmaking, in which a woman and a man are introduced to each other to consider the possibility of marriage. The term omiai is sometimes mistranslated as an "arranged marriage" but it can be described as a meeting opportunity with more serious considerations for the future as a process of courtship. According to the National Institute of Population and Social Security Research, in 2005 it was estimated that around 6.2% of marriages in Japan are arranged via omiai.

The practice of omiai emerged in 16th century Japan among the samurai classes, with the intention to form and protect strong military alliances among warlords to ensure mutual support. Later, during the Tokugawa period (1603–1868), the practice of omiai spread to other urban classes trying to emulate samurai customs. It became the practice for those seeking a union between families, and parents on both sides made all the decisions regarding marriage.

Omiai was a solemn practice and involved considerations that are not given as much weight by most modern Japanese people, such as family bloodlines and class. Nowadays, this type of omiai is usually seen portrayed more in films and television dramas.

After the Pacific War, the trend was to abandon the restrictive arranged-meetings system. In the 1930s and 40s, omiai practices accounted for 69% of marriages in Japan; by 2010 the figure had dropped to 5.2%. Modern forms of omiai are still practiced in Japan today by various marriage agencies; however, practices such as konkatsu or 'spouse hunting' have also emerged as alternatives to omiai for many single people who struggle to find a marriage partner, but might not want to go through a matchmaker. There have also been accounts of how parents pressure their unmarried children into arranged meetings that eventually lead to marriages, particularly with children who would assume family responsibilities such as those inheriting a family business.

In 2014, Japanese prime minister Shinzo Abe set aside ¥3 billion to help with omiai and konkatsu matchmaking efforts within Japan, as part of the Japanese governments efforts to increase the declining birth rate in Japan.

Historically, omiai signified that the parties were brought together expressly for the purpose of marriage on the initiative of the parents, a friend of the family, or a go-between. It also meant that the initial criteria of selection were objective ones. The potential spouse and their family met with the go-between (nakōdo) and examined all eligible persons. The nakōdo often had photographs of candidates and a rirekisho, a small personal history. The rirekisho frequently included the name, age, health, education, occupation and marital status of all members of the candidate's family.

The families then sat down with the nakōdo and screened the portfolios to eliminate any obviously inappropriate candidates. The photographs and rirekisho were then brought to the home of the potential spouse's family for the son or daughter to scrutinize. The participant and their family examined the photos and short personal histories based on an investigation of social consideration. The education level and occupations of the potential candidate's family were historically the first aspects taken into consideration at that meeting. The potential mate and their mother then created a list of primary choices and asked the nakōdo to investigate the first choice.

In more selective omiai, the candidates and their families were judged on a larger set of criteria aimed at determining the suitability and the balance of the marriage. These criteria are formally known in Japan as iegara (家柄). They included level of education, income, occupation, physical attractiveness, religion, social standing, and hobbies. The participant's bloodline (血統, kettō) also played a large role. Many were fearful of the possibility that a potential candidate's blood was contaminated with diseases such as epilepsy, neurosis, or mental illness. The fear was so prevalent that the Eugenic Protection Law of 1948 was passed to legalize sterilization and abortion for people with a history of mental defects and other hereditary diseases. Social status also played a large role in selecting a candidate. Ideally, paired candidates and their families would be of equal social status, so some candidates had a hard time finding a mate if their family was not of a certain social status. Family lineage also affected the quality of candidates historically; for example, a candidate with samurai blood was more likely to be picked than one with ancestry from a different class, especially during the Tokugawa era.