Mātā Sundarī (died 1747, Punjabi: ਮਾਤਾ ਸੁੰਦਰੀ) was a wife of Guru Gobind Singh. She led the Sikh community after the death of her husband.

She was the daughter of Ram Sarana, a Punjabi Soni Kumarāv Khatri of Bijwara Soni - in present-day Hoshiārpur district.In 1673 Sundari married Guru Gobind Singh. In 1688 she gave birth to Ajit Singh. In 1704, when the family of Guru Gobind Singh was forced to break up during the Battle of Sarsa, Mata Sundari and Mata Sahib Kaur dressed like ordinary village women and headed toward Ambala, hoping to find shelter, Nand Lal escorted them to Delhi using his good connections with powerful nobles, he protected them from Wazir Khan, the Mughal governor of Sirhind.

On 23 July, 1707, Mughal emperor Bahadur Shah met with Gobind Singh in order to engage in negotiations. The Guru was honored with gifts and Bahadur Shah sent one lakh rupees worth of jewelry, clothes, and ornaments to Sundari in Delhi.

Mata Sundari adopted a boy and named him after her late son, Ajit Singh. Later, he killed a Muslim beggar who had been receiving his generous alms every day. When the beggar persistently demanded an even greater gift, the situation became difficult, and Ajit Singh ended his life. He was arrested, tied to the tail of an elephant, and dragged through the streets of Delhi. At one sharp turn, the enraged elephant stepped on his head and crushed it. Mata Sundari then fled to Mathura, where the Raja of Jaipur gave her a new home and a handsome allowance. Meanwhile, her house and property in Delhi were seized by the Muslims.

In 1714, a resolute effort was envisaged by Farrukhsiyar to suppress Banda's rebellion, as he was evading capture despite significant Mughal endeavors and resource investments. Initially, Mata Sundari was asked to persuade Banda to cease his lawlessness and his expedition against the Mughals in exchange for jagirs and the recruitment of Sikh soldiers into the imperial army. However, Banda declined due to his lack of trust in the government. The Emperor then imprisoned both of Gobind's widows, prompting Sundari to write to Banda again, urging him to submit. Banda again declined, leading the Emperor to tighten restrictions on the widows, which culminated in the excommunication of Banda Singh Bahadur by Mata Sundari for refusing to submit to the Emperor as per her demands. She further accused him of assuming the role of "Guru" over the Sikhs and reprimanded his followers in a hukam-nama. This dispute led to the formation of two separate factions within the contemporary Sikh community: the Tat Khalsa, who were allied with Mata Sundari, and the Bandais, who were allied with Banda Singh Bahadur.

Mata Sundari's intervention led to approximately fifteen thousand of Banda's followers abandoning him prior to the Siege of Gurdas Nangal.

Disputes between the Tat Khalsa and the Bandais primarily included issues such as Banda's abandonment of the traditional blue robes in favor of red ones, his insistence on vegetarianism, his observance of caste rituals, and his replacement of the prescribed Sikh slogan with "Fateh Darshan." There were also concerns over the excesses committed by Banda's troops during their campaign of retribution against the Mughals. Banda's excommunication impeded his ability to counter the Mughals and contributed to his eventual capture and execution.

Modern Sikh tradition speaks of at least two different Khalsas: the Tat Khalsa—which adheres to the polity and injunctions of Guru Gobind Singh—and the Bandais, who adopted the principles of Banda Singh Bahadur.