  In this work, we have studied the variable stars in the young open cluster
NGC 1893 based on a multi-year photometric survey covering a sky area around
the cluster up to $31' \times 31'$ wide. More than 23\,000 images in the $V$
band taken from January 2008 to February 2017 with different telescopes,
complemented with 90 images in the $B$ band in 2014 and 2017, were reduced, and
light curves were derived in $V$ for 5653 stars. By analyzing these light
curves, we detected 147 variable stars (85 of them being new discoveries),
including 110 periodic variables, 15 eclipsing binaries and 22 non-periodic
variables. Proper motions, radial velocities, color-magnitude and two-color
diagrams were used to identify the cluster membership of these variable stars,
resulting in 84 members. Periodic variable members were then classified into
different variability types, mainly according to their magnitudes and to their
periods of variability, as well as to their positions in the
Hertzsprung-Russell diagram for the early-type stars. As a result, among
main-sequence periodic variable members, we identified five $\beta$ Cep
candidates, seven slowly pulsating B-type candidates, and thirteen
fast-rotating pulsating B-type (FaRPB) candidates (one of which is a confirmed
classical Be star). While most of the FaRPB stars display properties similar to
the ones discovered in NGC 3766 by Mowlavi et al. (2013), five of them have
periods below 0.1~d, contrary to expectations. Additional observations,
including spectroscopic, are called for to further characterize these stars. We
also find a binary candidate harboring a $\delta$-Scuti candidate.
