Better still is a simple series diode plus current-limit resistor.

simulate this circuit – Schematic created using CircuitLab
There can be advantages to putting a reverse-polarity diode in parallel with a LED when that LED is being fed from an AC source but there are usually specific reasons for doing so.
The problem with a single series resistor feeding a LED with a reverse-polarity diode in parallel is that the resistor is dissipating power for most of the entire AC half-cycle.
If you use a series resistor plus a diode also in series, the resistor is dissipating power for only half of the time. This reduces the power by half and either lets you use a smaller resistor OR the resistor runs cooler.
You can add a resistor in parallel with the LED if you want to trim the turn-on voltage of the LED. This can help stop the LED from illuminating with small leakage currents.