  The duration and fidelity of qubit readout is a critical factor for
applications in quantum information processing as it limits the fidelity of
algorithms which reuse qubits after measurement or apply feedback based on the
measurement result. Here we present fast multiplexed readout of five qubits in
a single 1.2 GHz wide readout channel. Using a readout pulse length of 80 ns
and populating readout resonators for less than 250 ns we find an average
correct assignment probability for the five measured qubits to be $97\%$. The
differences between the individual readout errors and those found when
measuring the qubits simultaneously are within $1\%$. We employ individual
Purcell filters for each readout resonator to suppress off-resonant driving,
which we characterize by the dephasing imposed on unintentionally measured
qubits. We expect the here presented readout scheme to become particularly
useful for the selective readout of individual qubits in multi-qubit quantum
processors.
