St Vincent is the name under which the American singer-songwriter Annie Clarke records and performs. It is also the name of her fourth album, from which this song is taken.
Reviewing it for the Guardian, Alex Petridis said:
Prince Johnny is a fascinating puzzle: it's hard to work out whether the titular character is male or female, whether or not the song's narrator has slept with him or her, or how much their affection is tinged with contempt.
In fact, the words are often ambiguous ... but they're the only thing here that is: bold, poised, precise without sounding sterile, St Vincent seems to be a straightforward triumph.