23S rRNA (cytosine<sup>1962</sup>-C<sup>5</sup>)-methyltransferase (, RlmI, rRNA large subunit methyltransferase I, YccW) is an enzyme with systematic name S-adenosyl-L-methionine:23S rRNA (cytosine<sup>1962</sup>-C<sup>5</sup>)-methyltransferase. This enzyme catalyses the following chemical reaction
The enzyme specifically methylates cytosine<sup>1962</sup> at C<sup>5</sup> in 23S rRNA.