The Tequesta tribe occupied the Miami area for around 2,000 years before contact with Europeans. A village of hundreds of people, dating to 500–600 B.C., was located at the mouth of the Miami River. It is believed that the entire tribe migrated to Cuba by the mid-1700s.

In 1566, admiral Pedro Menéndez de Avilés, Florida's first governor, claimed the area for Spain. A Spanish mission was constructed one year later. Spain and Britain successively ruled Florida until Spain ceded it to the United States in 1821. In 1836, the U.S. built Fort Dallas on the banks of the Miami River as part of its development of the Florida Territory and its attempt to suppress and remove the Seminoles. As a result, the Miami area became a site of fighting in the Second Seminole War.

Miami is noted as the only major city in the United States founded by a woman. Julia Tuttle, a local citrus grower and a wealthy Cleveland native, was the original owner of the land upon which the city was built. In the late 19th century, the area was known as "Biscayne Bay Country", and reports described it as a promising wilderness and "one of the finest building sites in Florida". The Great Freeze of 1894–95 hastened Miami's growth, as the crops there were the only ones in Florida that survived. Julia Tuttle subsequently convinced railroad tycoon Henry Flagler to extend his Florida East Coast Railway to the region, for which she became known as "the mother of Miami". Miami was officially incorporated as a city on July 28, 1896, with a population of just over 300. It was named for the Miami River, derived from Mayaimi, the historic name of Lake Okeechobee and the Native Americans that lived around it.

African American labor played a crucial role in Miami's early development. During the early 20th century, migrants from the Bahamas and African-Americans constituted 40 percent of the city's population.^:25 Despite their role in the city's growth, their community was limited to a small space. When landlords began to rent homes to African-Americans around Avenue J (what would later become NW Fifth Avenue), a gang of white men with torches marched through the neighborhood and warned the residents to move or be bombed.^:33

Miami prospered during the 1920s with an increase in population and infrastructure as northerners moved to the city. The legacy of Jim Crow was embedded in these developments. Miami's chief of police at the time, H. Leslie Quigg, did not hide the fact that he, like many other white Miami police officers, was a member of the Ku Klux Klan. Unsurprisingly, these officers enforced social codes far beyond the written law. Quigg, for example, "personally and publicly beat a colored bellboy to death for speaking directly to a white woman".^:53

The collapse of the Florida land boom of the 1920s, the 1926 Miami Hurricane, and the Great Depression in the 1930s slowed development. When World War II began, Miami became a base for U.S. defense against German submarines due to its prime location on the southern coast of Florida. This brought an increase in Miami's population; 172,172 people lived in the city by 1940. The city's nickname, The Magic City, came from its rapid growth, which was noticed by winter visitors who remarked that the city grew so much from one year to the next that it was like magic.

After Fidel Castro rose to power in Cuba following the Revolution in 1959, many wealthy Cubans sought refuge in Miami, further increasing the city's population. Miami developed new businesses and cultural amenities as part of the New South in the 1980s and 1990s. At the same time, South Florida weathered social problems related to drug wars, immigration from Haiti and Latin America, and the widespread destruction of Hurricane Andrew. Racial and cultural tensions sometimes sparked, but the city developed in the latter half of the 20th century as a major international, financial, and cultural center. It is the second-largest U.S. city with a Spanish-speaking majority (after El Paso, Texas), and the largest city with a Cuban-American plurality.

The city proper is home to less than one-thirteenth of the population of South Florida. Miami is the 42nd-most populous city in the United States. The Miami metropolitan area, however, which includes Miami-Dade, Broward and Palm Beach counties, had a combined population of more than 5.5 million people, ranked seventh largest in the United States, and is the largest metropolitan area in the southeastern United States. As of 2008, the United Nations estimates that the Miami Urban Agglomeration is the 44th-largest in the world.

In 1960, Hispanics made up about 5% of the population of Miami-Dade County. Between 1960 and 2000, 90% of the population growth in the county was made up of Hispanics, raising the Hispanic portion of the population to more than 57% by 2000.

In 1970, the Census Bureau reported Miami's population as 45.3% Hispanic, 32.9% non-Hispanic White, and 22.7% Black. Miami's explosive population growth has been driven by internal migration from other parts of the country, primarily up until the 1980s, as well as by immigration, primarily from the 1960s to the 1990s. Today, immigration to Miami has continued and Miami's growth today is attributed greatly to its fast urbanization and high-rise construction, which has increased its inner city neighborhood population densities, such as in Downtown, Brickell, and Edgewater, where one area in Downtown alone saw a 2,069% increase in population in the 2010 Census. Miami is regarded as more of a multicultural mosaic, than it is a melting pot, with residents still maintaining much of, or some of their cultural traits. The overall culture of Miami is heavily influenced by its large population of Hispanics from the Caribbean and South America and black people mainly from the Caribbean islands.

Miami has a minority-majority population, as non-Hispanic whites comprise less than half of the population, 11.9%, down from 41.7% in 1970. Hispanic or Latino (of any race) make up 70% of Miami's population. As of the 2010 census, the racial makeup of the population of Miami was 72.6% White American (including White Hispanic), 19.2% Black or African American, 1% Asian American, and the remainder belonged to other groups or was of mixed ancestry.

The 2010 US Census reported that the Hispanic population in Miami accounted for 70% of its total population, with 34.4% of city residents being of Cuban origin, 15.8% had a Central American background (7.2% Nicaraguan, 5.8% Honduran, 1.2% Salvadoran, and 1.0% Guatemalan), 8.7% were of South American descent (3.2% Colombian, 1.4% Venezuelan, 1.2% Peruvian, 1.2% Argentine, 1.0% Chilean and 0.7% Ecuadorian), 4.0% had other Hispanic or Latino origins (0.5% Spaniard), 3.2% descended from Puerto Ricans, 2.4% were Dominican, and 1.5% had Mexican ancestry.

As of 2010, those of African ancestry accounted for 19.2% of Miami's population. Of the city's total population, 5.6% were West Indian or Afro-Caribbean American origin (4.4% Haitian, 0.4% Jamaican, 0.4% Bahamian, 0.1% British West Indian, and 0.1% Trinidadian and Tobagonian, 0.1% Other or Unspecified West Indian), 3.0% were Black Hispanics, and 0.4% were Subsaharan African origin.

As of 2010, those of (non-Hispanic white) European ancestry accounted for 11.9% of Miami's population. Of the city's total population, 1.7% were German, 1.6% Italian, 1.4% Irish, 1.0% English, 0.8% French, 0.6% Russian, and 0.5% were Polish. Since the 1960s, there has been massive white flight with many non-Hispanic whites moving outside Miami due to the influx of immigrants settling in most parts of Miami.

As of 2010, those of Asian ancestry accounted for 1.0% of Miami's population. Of the city's total population, 0.3% were Indian people/Indo-Caribbean American (1,206 people), 0.3% Chinese (1,804 people), 0.2% Filipino (647 people), 0.1% were other Asian (433 people), 0.1% Japanese (245 people), 0.1% Korean (213 people), and 0.0% were Vietnamese (125 people).

In 2010, 1.9% of the population considered themselves to be of only American ancestry (regardless of race or ethnicity), while 0.5% were of Arab ancestry, as of 2010.

According to a 2014 study by the Pew Research Center, Christianity is the most prevalently practiced religion in Miami (68%), with 39% professing attendance at a variety of churches that could be considered Protestant, and 27% professing Roman Catholic beliefs. followed by Judaism (9%); Islam, Buddhism, Hinduism, and a variety of other religions have smaller followings; atheism or no self-identifying organized religious affiliation was practiced by 21%.

There has been a Norwegian Seamen's church in Miami since the early 1980s. In November 2011, Crown Princess Mette-Marit opened a new building for the church. The church was built as a center for the 10,000 Scandinavians that live in Florida. Around 4,000 of them are Norwegian. The church is also an important place for the 150 Norwegians that work at Disney World.

As of 2016, a total of 73% of Miami's population age five and over spoke a language other than English at home. Of this 73%, 64.5% of the population only spoke Spanish at home while 21.1% of the population spoke English at home. About 7% spoke other Indo-European languages at home, while about 0.9% spoke Asian languages or Pacific Islander languages/Oceanic languages at home. The remaining 0.7% of the population spoke other languages at home.

As of 2010, 70.2% of Miami's population age five and over spoke only Spanish at home while 22.7% of the population spoke English at home. About 6.3% spoke other Indo-European languages at home. About 0.4% spoke Asian languages or Pacific Islander languages/Oceanic languages at home. The remaining 0.3% of the population spoke other languages at home. In total, 77.3% spoke another language other than English.

As of 2010, 80% of people over age 25 were a High School graduate or higher. 27.3% of people in Miami had a bachelor's degree or higher.

As of 2010, there were 158,317 households, of which 14.0% were vacant. 22.7% had children under the age of 18 living with them, 31.3% were married couples living together, 18.1% have a female head of household with no husband present, and 43.1% were non-families. 33.3% of all households were made up of individuals, and 11.3% had someone living alone who was 65 years of age or older (4.0% male and 7.3% female.) The average household size was 2.47 and the average family size was 3.15.

In 2010, the city population was spread out, with 18.8% under the age of 18, 9.4% from 18 to 24, 33.1% from 25 to 44, 25.0% from 45 to 64, and 13.6% who were 65 years of age or older. The median age was 38.8 years. For every 100 females, there were 99.2 males. For every 100 females age 18 and over, there were 98.1 males.

In 2010, 58.1% of the county's population was foreign born, with 41.1% being naturalized American citizens. Of foreign-born residents, 95.4% were born in Latin America, 2.4% were born in Europe, 1.4% born in Asia, 0.5% born in Africa, 0.2% in North America, and 0.1% were born in Oceania.

In 2004, the United Nations Development Program (UNDP) reported that Miami had the highest proportion of foreign-born residents of any major city worldwide (59%), followed by Toronto (50%).

About 22.2% of families and 27.3% of the population were below the poverty line at the census, including 37.1% of those under age 18 and 32.8% of those aged 65 or over.