Alexandre Dimitri Song Billong (born 9 September 1987), better known as Alex Song, is a Cameroonian footballer who plays for FC Barcelona in La Liga and the Cameroon national team. He plays as a central or defensive midfielder, and can also play as a central defender.

He is the cousin of former footballer Rigobert Song.

Originally a utility player on the fringes of the first team, Song quickly became an integral part of Arsenal's starting eleven during the preseason to the 2008–09 campaign. He played for Cameroon in 2010 FIFA World Cup. Song was called up for the 2010 Africa Cup of Nations and was the only Cameroonian named in the Team of the Tournament. Known for his colourful hair dye, Song also possesses a French passport.

Song was born in Douala, Cameroon and lost his father at the age of three. Since then, his cousin Rigobert Song has been like a second father and was a major influence in choosing football as a career. Unable to find a club or academy where he could hone his skills, Petit Song, as he is known in the Cameroon side, opted to move to France, joining SC Bastia at the age of 16. One of the players who inspired Song the most when he was young was Michael Essien.

Song wanted to give his children a good upbringing in life, which he claims eluded him; he married at the age of 18 and is now father to two children, the older being two-year-old Nolan. Song is one of 28 children in his family; he has 17 sisters and 10 brothers.

In 2011, Song became an ambassador for Grassroot Soccer, an international non-profit organisation working through football to stop the spread of HIV.

Song was first capped by Cameroon in 2005. He was named in the Cameroon squad for the 2008 Africa Cup of Nations. He played for Cameroon in their first group match, a 4–2 defeat against holders Egypt; he replaced Stéphane Mbia at half time, joining his cousin Rigobert on the pitch.

For the duration of the tournament he was a revelation in defence for Cameroon, earning a Man of the Match award in Cameroon's semi final, but then going off injured in the final against Egypt. He was nonetheless named in the Tournament Best XI, alongside Newcastle midfielder and compatriot Geremi.

Song was called up for the 2010 Africa Cup of Nations and was the only Cameroonian named in the Team of the Tournament.

Song was included in the Cameroonian squad for the 2010 FIFA World Cup in South Africa. He did not appear in his side's opening loss to Japan, but played the full 90 in Cameroon's disappointing 2–1 loss to Denmark.

The result ensured that Les Lions were the first country eliminated from the World Cup. He was an unused substitute in Cameroon's final group stage match against the Netherlands, a 2–1 loss, but his cousin Rigobert made his final national team appearance in the match.