Deputy President Kgalema Motlanthe.
"The ANC Youth League wishes President Kgalema Motlanthe a joyous and productive birthday," read the statement issued by league spokesperson Khusela Sangoni-Khawe.
She could not immediately be reached for comment on the choice of the word "president".
In June, the youth league sent birthday congratulations to former president Thabo Mbeki. He replied with a letter of thanks.
The league did not officially extend birthday wishes to President Jacob Zuma on his 70th birthday on April 12.
Zuma defeated Mbeki in the ANC's December 2007 leadership race in Polokwane, following intense campaigning for Zuma by the youth league. The league and Zuma have clashed since then.
In their wishes, the league described Motlanthe him as a "politically, organisationally and ideologically sound leader of the ANC.
"He is also not one to sacrifice principle at the altar of expediency," read the statement.
The league called Motlanthe a "principled leader" with a "strong Christian upbringing" and gave him their endorsement for "when the time comes in the next few months".
"We are confident that the very values of principle, integrity and humility that define him will, when the time comes in the next few months, guide him in the execution of the mandate that the overwhelming majority of ANC members will bestow upon him," it said. – Sapa