An oscillator includes a first container, a second container accommodated in the first container, a resonator element accommodated in the second container, a temperature sensor accommodated in the second container, a first circuit element that is accommodated in the second container and includes an oscillation circuit that causes the resonator element to oscillate so as to generate an oscillation signal on which temperature compensation is performed based on a detected temperature of the temperature sensor, and a second circuit element that is accommodated in the first container and includes a frequency control circuit that controls a frequency of the oscillation signal. The second container and the second circuit element are stacked.