The Al-Istiqamah Mosque (Malay: Masjid Al-Istiqamah) is a mosque in Serangoon, Singapore which was completed in 1999. It is located at Serangoon North Estate, at the corner of Yio Chu Kang Road and Ang Mo Kio Avenue 3, with the front entrance at Serangoon North Avenue 2.

As one of the mosques built under the Mosque Building & Mendaki Fund scheme headed by Majlis Ugama Islam Singapura (MUIS), it is named after virtuous qualities as a continuation from the first one, that being Masjid Al-Khair (The Good). Initially, the name "As-Sobr" (The Patient) was suggested for this mosque, but after consultation with a few local Islamic scholars, the name "Al-Istiqamah" (The Constant) was ultimately chosen.

Masjid Al Istiqamah is the second mosque to be built under Phase 3 of the Mosque Building & Mendaki Fund scheme headed by MUIS.

The plot for the mosque building was bought on 12 August 1992 with the fund raising arm of the Mosque Building Committee formed in June 1995. The estimated amount needed was S$700,000 for the basic requirements in the initial stage of building. So few people came forward to volunteer their services that an advertisement had to be put out in the Berita Harian newspaper.

The cost of building the mosque was estimated at around $5 million.

Construction of the mosque began in September 1997. On 11 June 1999, Masjid Al-Istiqamah was declared as a waqf (vested property) and was officially accessible to the Muslim members of the public. The purchase of land and construction of the mosque cost an estimated $7 million in total.

On 17 June 2000, Masjid Al-Istiqamah held an opening ceremony which was attended by Mohamad Maidin Packer Mohd, Member of Parliament for Marine Parade Group Representation Constituency. Then in September 2000, with the official appointment of its first Mosque Manager, it became the first mosque in Singapore to have its office administration 'fully accommodated' for the congregation with its opening hours from 8:30 to 22:30 including Saturdays, Sundays and public holidays. The mosque's office closes only on the first two days of Shawwal, during the Aidilfitri celebrations.

As of 2025, the mosque is currently undergoing a renovation and upgrading to improvise its facilities.

Architect firm James Yip and Partners designed the mosque.

The three-storeyed mosque with a combination of designs from the Nusantara, Middle East and Mauritius can cater to a maximum of 3,300 worshippers at any one time. Its convertible concept enables the optimisation of space and multiple functionalities of the rooms.

The building is divided into two general areas, via the i'tikaf section occupying the 'front' portion, and the multi-purpose section making up the 'rear'. The i'tikaf area which is roofed by solid timber can accommodate about 480, 330 and 270 worshippers on levels one, two and three respectively.

The nearest MRT station to the mosque is the Hougang MRT station. Various bus services also lead to the mosque.

• Islam in Singapore
• List of mosques in Singapore

• Official website of the Al-Istiqamah Mosque