We report an intensiometric, near-infrared (NIR) fluorescent, genetically encoded calcium ion (Ca
2+
) indicator (GECI) with excitation and emission maxima at 678 nm and 704 nm, respectively. This GECI, designated NIR-GECO1, enables imaging of Ca
2+
transients in cultured mammalian cells and brain tissue with sensitivity comparable to currently available visible-wavelength GECIs. We demonstrate that NIR-GECO1 opens up new vistas for multicolor Ca
2+
imaging in combination with other optogenetic indicators and actuators.
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