Despite being robotic lifeforms with generally non-sexual methods of reproduction, the Transformer species has almost always been shown to include both male and female gender analogues, at least mentally if not physically.
Female Transformers were originally depicted as an anomaly, specifically called outas either a thought-to-be-extinct subgroup or simply never existing in the first place. Thanks, 1980s! Always so sensitive! Well into the third decade of the brand, the number of female characters to have received either mass retail toy releases or recurring cartoon appearances was still in the single digits... and some of those had been originally designed as toys for male characters or were portrayed as male in some cartoon markets. While they are still comparatively rare, as the years went on they have increased greatly in numbers, prominence, and overall fairness of representation, and are considered an official part of the Transformers brand in pretty much every continuity. Nowadays, female Transformers are basically considered a normal part of the Cybertronian population.
There's still a long way to go, since they ARE still uncommon compared to the "guys" and as Mairghread Scott pointed out, this can inadvertently make any given female Transformer and their stories seem like a comment on real women. That's part of a way bigger argument for gender equality in entertainment and society at large that's a bit beyond this wiki's scope to fully explore.
A list of female Transformers from all continuities is available.
Well, I remember bringing up that question early on with Hasbro, "are any of these female?" And then I think Hasbro's attitude was, "this is a boy toy. We don't wanna have, you know, girl robots." So, I said, "OK, just want to clarify that."