What is the Sikh initiation ceremony into the Khalsa called?

The Sikh initiation ceremony into the Khalsa is called amrit sanchar.

Amrit sanchar is the formal initiation ceremony through which a Sikh enters the Khalsa. The ceremony uses amrit, prepared by stirring water and sugar crystals with a double-edged sword while sacred recitations are performed. A group of five initiated Sikhs, known as the Panj Pyare, traditionally administers the ceremony. Initiates commit themselves to Sikh discipline and to living according to the Khalsa code of conduct.

The ceremony is associated with Guru Gobind Singh’s creation of the Khalsa at Anandpur in 1699. Initiated Sikhs traditionally adopt the names Singh for men and Kaur for women and observe the Five Ks. Amrit sanchar is not the same as Anand Karaj, the Sikh marriage ceremony. It is also distinct from Ardas, a supplication recited in many contexts, and Akhand Path, the uninterrupted reading of the Guru Granth Sahib.