  We report the discovery of a new bright (V$\sim$12.6) cataclysmic variable
star identified with the ROSAT X-ray source RX J1643.7+3402. Spectroscopic and
photometric observations show it to be a novalike variable sharing some of the
characteristics of the SW Sex sub-class of novalike CVs. The spectroscopic
period may be either 2\fh575 or 2\fh885, within the period "gap." A photometric
modulation with a probable period of 2\fh595 and an amplitude of $\sim$ 0.1 mag
in V is present on most nights and could be either a "positive" or a "negative"
superhump modulation (depending on the exact spectroscopic period), indicating
the presence of a precessing accretion disk in this system. Rapid variations of
0.1 to 0.2 mag amplitude in V repeat with a time scale of $\sim$ 15 min.
