An IPA (India Pale Ale) is an ale, not a lager. Ales are fermented with top-fermenting yeast at warmer temperatures, and major style guides place British-style, American-style, West Coast, and hazy IPAs under ale categories.
Lagers use bottom-fermenting yeast and colder fermentation. Brewers do make hoppy India Pale Lager (IPL) beers, but those are classified separately as lager styles—not as classic IPAs. Source: Brewers Association Beer Style Guidelines.