June is the sixth month of the year in the Julian and Gregorian calendars—the latter the most widely used calendar in the world. Its length is 30 days. June succeeds May and precedes July. This month marks the start of summer in the Northern Hemisphere and contains the summer solstice, which is the day with the most daylight hours. In the Southern Hemisphere, June is the start of winter and contains the winter solstice, the day with the fewest hours of daylight out of the year.

In places north of the Arctic Circle, the June solstice is when the midnight sun occurs, during which the Sun remains visible even at midnight. The Atlantic hurricane season—when tropical or subtropical cyclones are most likely to form in the north Atlantic Ocean—begins on 1 June and lasts until 30 November. Several monsoons and subsequent wet seasons also commence in the Northern Hemisphere during this month. Multiple meteor showers occur annually in June, including the Arietids, which are among the most intense daylight meteor showers of the year; they last between 22 May and 2 July, peaking in intensity on 8 June.

Numerous observances take place in June. Midsummer, the celebration of the summer solstice in the Northern Hemisphere, is celebrated in several countries. In Catholicism, this month is dedicated to the devotion of the Sacred Heart of Jesus, and known as the Month of the Sacred Heart. In the United States, June is dedicated to Pride Month, a month-long observance of the LGBTQ community. Father's Day, which honours fathers and fatherhood, occurs on the third Sunday in June in most countries.