Cantonment MRT station is a future underground Mass Rapid Transit (MRT) station on the Circle line (CCL), situated in Bukit Merah planning area, Singapore, along Everton Road near the junction of Spottiswoode Park Road. This station is part of Stage 6 of the Circle line which will "close the circle" between the HarbourFront and Marina Bay stations.

The station is built underneath and will be integrated with the historic Tanjong Pagar railway station, which ceased operations on 1 July 2011. Cantonment station will provide MRT access to the future Greater Southern Waterfront development. The station was to be opened in 2025 along with the other CCL6 stations, but was delayed to 2026 due to the COVID-19 pandemic.

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Artist impression of Cantonment station Source: LTA

The station was first announced on 29 October 2015 as part of the Stage 6 of the Circle line. Contract 883 for the construction of Cantonment station was awarded to China State Construction Engineering Corporation Limited (Singapore Branch) at a sum of S$205 million (US$148.45 million) in November 2017. Construction began that year, with expected completion in 2026.

In November 2017, the old train platform canopy structures were relocated to facilitate construction works of the station to a restoration yard nearby. In March 2018, the Land Transport Authority (LTA) has temporarily dismantled part of the platforms in Tanjong Pagar railway station to make way for the construction of Cantonment MRT station and is working with a heritage consultant and members of the heritage community on possible solutions for the affected platforms. In September 2020, the Sun Wu TBM managed to tunnel underneath the old Tanjong Pagar Railway station building.

Tunnelling works for the CCL6 were completed on 12 January 2022, with a final tunnel breakthrough from Prince Edward Road station into this station. The tunnels between this station and the adjacent Prince Edward Road station were constructed only 6.7 metres (22 ft) below the former Tanjong Pagar Railway Station. Prior to the tunnelling works, an extensive survey was conducted to ensure that the tunnels do not cross through the building's foundations. Structures were erected to protect the railway station's facade and interior, and monitoring instruments were installed to watch out for any building settlement. To construct the tunnels to Keppel station, the Keppel viaduct had to be closely monitored while underpinning the viaduct with new micro piles. Three bored piles were removed for the tunnelling works.

In March 2024, the platform canopy shelters were restored to their original places via self-propelled modular transporters that were typically used to lift heavy loads at construction sites. Previously cut during the dismantlement, they were stitched together with new steel reinforcement bars embedded in concrete.

When completed, the station is expected to be integrated with the Tanjong Pagar railway station. The affected canopy structures is expected to be reinstated to their original locations once the station is finished. The size of the station will be 162 metres (531 ft) by 50 metres (160 ft) by 27 metres (89 ft) with three levels.

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