The Save the Children issued the report, called Every Last Girl, on October 11 to mark International Day of the Girl Child.
The report says a girl under 15 is forced into marriage every seven seconds and that many girls only 10 years of age are being forced to marry.
Save the Children says early marriage can trigger a cycle of disadvantage across every part of a girl's life.
The report says early marriage for girls usually prevents them from getting an education, from seeking work, and often continues a cycle of poverty.
Conflict, poverty and humanitarian crises are seen as major factors that leave girls exposed to child marriage.
The study ranks 144 countries on its treatment of girls. It ranks them based on the hardest place to be a girl based on schooling, child marriage, teen pregnancy, maternal deaths and the number of women in parliament.
Tajikistan was 57th on the list. Azerbaijan (69th), Georgia (62nd), and Kyrgyzstan (59th) were also rather low in the rankings. Belarus (24th) and Kazakhstan (30th) were placed high on the list.
The worst countries in which to be a girl are Somalia, Mali, Central African Republic, Chad and Niger, which all ranked at the bottom of the Girls' Opportunity Index.
Countries at the top include Sweden, Finland, Norway, Netherlands and Belgium.
About 14 million girls under the age of 18 are ensnared by child marriage every year, according to the United Nations children's agency UNICEF. It estimates the number of women married before their 18th birthday will grow from more than 700 million women today to around 950 million by 2030.
Some 62 million girls around the world are not in school, according to the US Agency for International Development.
International Day of the Girl Child is an international observance day declared by the United Nations; it is also called the Day of the Girl and the International Day of the Girl. October 11, 2012, was the first Day of the Girl. The observation supports more opportunity for girls and increases awareness of many issues and inequalities faced by girls around the world. Many global development plans do not include or consider girls, and their issues and problems become invisible. More than 62 million girls around the world reportedly have no access to education. Worldwide and collectively, girls ages 5 to 14 spend more than 160 million hours more on household chores than boys of the same age do. Globally, one in four girls is married before age 18.
The Day of the Girl helps raise awareness not only of the issues that girls face, but also what is likely to happen when those problems are solved. For example, educating girls helps reduce the rate of child marriage, disease and helps strengthen the economy by helping girls have access to higher paying jobs.
