Almarhumah Enche’ Besar Hajah Khalsom binti Abdullah (Jawi: انچئ بسر حاجه كلثوم بنت عبد الله; born Josephine Ruby Trevorrow; 2 December 1935 – 1 June 2018) was the first wife of Sultan Iskandar[1] and mother of Sultan Ibrahim, who is the current Sultan of Johor and the seventeenth Yang di-Pertuan Agong (King of Malaysia) since 31 January 2024.

After that she converted to Islam and changed her name to Khalsom binti Abdullah; they married on 5 January 1956.

On 8 May 1959, after her husband was proclaimed Tunku Mahkota (Crown Prince) of Johor, she was known as Yang Amat Mulia Che’ Puan Khalsom Abdullah.

This royal couple had four children: On 9 June 1962 they divorced, shortly after Iskandar's second marriage to Tengku Zanariah, and she returned to England.

[2] Later in 2010, her son Ibrahim, who had just become the Sultan of Johor, bestowed upon her the honorific form of address as Yang Amat Mulia Enche’ Besar Hajah Khalsom Abdullah, D.K., S.M.I.J.