"Head over heels in love" is an expression that is commonly used to describe a state of extreme affection or infatuation. However, there are several synonyms that can be used to convey a similar sentiment. The phrase "smitten" is a commonly used synonym, which suggests being deeply affected or charmed by someone. Another alternative could be "besotted", which implies being completely captivated or enamored with someone. Other synonyms include "infatuated", "enamored," "captivated," "obsessed" and "madly in love." Each of these synonyms offers a slightly different nuance, but all communicate the intensity of emotional attachment that "head over heels" suggests.