| Consort: | yes |
| Bahiyah Malay: {{Script|Arab|باهية | |
| Succession: | Raja Permaisuri Agong |
| Reign: | 21 September 1970 – 20 September 1975 |
| Coronation: | 20 February 1971 |
| Cor-Type: | Malaysia |
| Predecessor: | Tengku Intan Zaharah |
| Successor: | Tengku Zainab |
| Succession1: | Sultanah of Kedah |
| Reign1: | 15 July 1958 – 26 August 2003 |
| Coronation1: | 20 February 1959 |
| Cor-Type1: | Installation |
| Predecessor1: | Sultanah Asma |
| Successor1: | Sultanah Haminah |
| Issue: |
|
| Father: | Tuanku Abdul Rahman ibni Almarhum Tuanku Muhammad |
| Mother: | Tunku Kurshiah binti Almarhum Tunku Besar Burhanuddin |
| Full Name: | Tunku Bahiyah binti Tunku Abdul Rahman |
| Regnal Name: | Sultanah Bahiyah binti Almarhum Tuanku Abdul Rahman |
| House: | Pagaruyung Mahawangsa (by marriage) |
| Birth Date: | 24 August 1930 |
| Birth Place: | Seri Menanti, Negeri Sembilan |
| Death Place: | Istana Kuala Cegar, Alor Setar, Kedah |
| Date Of Burial: | 27 August 2003 |
| Place Of Burial: | Kedah Royal Mausoleum, Alor Setar, Kedah |
| Religion: | Sunni Islam |
Sultanah Hajah Bahiyah binti Almarhum Tuanku Abdul Rahman (Malay: سلطانة حاجة باهية بنت المرحوم توانكو عبدالرحمن|label=[[Jawi alphabet|Jawi]]|script=arab|italic=unset; 24 August 1930 – 26 August 2003) was the Sultanah of Malaysian State of Kedah from 1958 until her death in 2003 and served as the fifth Raja Permaisuri Agong of Malaysia from 21 September 1970 until 20 September 1975.
Tunku Bahiyah was born on 24 August 1930 in Seri Menanti, Negeri Sembilan. She was the eldest daughter of Tuanku Abdul Rahman and his third wife Tunku Kurshiah, the Yang di-Pertuan Besar and the Tunku Ampuan Besar of Negeri Sembilan, who were then elected as the first Yang di-Pertuan Agong and Raja Permaisuri Agong of Malaysia.
She received her education at a Malay School in Seri Menanti and the Seremban Convent School. She later furthered her studies in the United Kingdom and received a degree in Social Science from University of Nottingham.
Tunku Bahiyah married Abdul Halim of Kedah in 1956. The royal couple adopted the twin daughters of Tunku Hamidah (Tuanku Abdul Halim's eldest sister), Tunku Soraya and Tunku Sarina (born 30 April 1960, adopted 3 May 1960). Bahiyah gave birth to a daughter, Tunku Puteri Intan Safinaz, on 22 July 1966.
Tunku Soraya would go on to marry Raja Iskandar Dzurkarnain (the current Raja Di-Hilir of Perak) in 1986. Tunku Sarina passed away on 31 August 1991.
In 1958, Tuanku Abdul Halim became Sultan of Kedah. Tunku Bahiyah was installed as the Sultanah of Kedah on his ascension to the throne.
From 1970 to 1975, she served her five-year term as Raja Permaisuri Agong of Malaysia when Tuanku Abdul Halim became the fifth Yang di-Pertuan Agong.
She died in her sleep at 12:23 pm of cancer and old age on 26 August 2003 at Istana Kuala Cegar, Alor Setar. She was laid to rest at the Langgar Royal Mausoleum in Alor Setar.
Sultanah Bahiyah was conferred various awards, both locally and abroad. In 1970, Emperor Hirohito of Japan awarded her the First Class of the Order of the Sacred Treasure. Later in the same year, President Suharto of Indonesia awarded her the First Class of the Order of the Star of Mahaputera.
In 1973, King Bhumibol Adulyadej of Thailand awarded her the Grand Cross of the Order of Chula Chom Klao.
Sultanah Bahiyah was awarded an Honorary Doctorate in Education by the University of Malaya where she served as the Chancellor from 1972 until 1986.
The general hospital in Alor Setar which is also the main referral and tertiary health centre in Northern Peninsular Malaysia was renamed in her honour to Sultanah Bahiyah Hospital.
There is a highway in Alor Setar, Sultanah Bahiyah Highway (Federal Route 255) was named after her.
SMK Sultanah Bahiyah, a secondary school in Alor Setar was named after her.
Sultanah Bahiyah Mosque, a mosque in Alor Setar was named after her.
Sultanah Bahiyah Library of Universiti Utara Malaysia was named after her.
Tuanku Bahiyah Residential College, a residential college at University of Malaya, Kuala Lumpur was named in honour of her.
Tuanku Hajah Bahiyah was the patron of various organisations such as:
See also: List of honours of the Kedah Royal Family by country.
She has been awarded:
Indonesia:
Japan:
Thailand: