Kesatuan ragbi, dikenali ramai sebagai ragbi, ialah sukan berpasukansentuh penuh yang asalnya dari England pada separuh pertama abad ke-19. Salah satu dua kodbola sepak ragbi, sukan ini berdasarkan berlari dengan bola di tangan. Dalam bentuk paling umumnya, sebuah permainan dimain antara dua pasukan 15 pemain menggunakan sebiji bola berbentuk bujur pada sebuah padang segi empat tepat yang dipanggil lapangan (pitch). Padang mempunyai tiang gol berbentuk H pada kedua-dua hujung.
Kesatuan ragbi ialah sukan yang popular di seluruh dunia, dimain oleh pemain lelaki dan wanita dari segenap umur. Peraturan tidak berbeza antara jantina. Pada tahun 2014, terdapat lebih daripada 6 juta orang bermain di seluruh dunia, 2.36 juta daripadanya pemain berdaftar. Ragbi Dunia, sebelum ini dipanggil Lembaga Bola Sepak Ragbi Antarabangsa (IRFB) dan Lembaga Ragbi Antarabangsa (IRB), telah menjadi badan pentadbir bagi kesatuan ragbi sejak tahun 1886, dan kini mempunyai 101 negara sebagai anggota penuh dan 18 anggota bersekutu.
^As of 2014 the International Rugby Board, now known as World Rugby, removed the total breakdown of world-wide player numbers by country, by age and sex to publish instead an overall figure per country. This document, titled '119 countries... 6.6 million players' adds the number of registered and unregistered players reported by each country. Some unions only report their registered players, i.e. those who play for an affiliated club or region. Other unions, such as England's Rugby Football Union, also report people taking part in outreach and educational programs, or unregistered players. In the 2012 figures reported by the RFU they reported 1,990,988 people playing rugby in England, including 1,102,971 under 13s, 731,685 teens and 156,332 seniors. Some of those recorded would have experienced rugby via educational visits to schools, playing tag or touch rugby, rather than playing regularly for a club. The figures released in 2014 give an overall figure of those playing rugby union, or one of its variants, as 6,684,118, but also reports that of that total, 3.36 million are registered players, while 4.3 million are unregistered.
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