Could Rex be the perfect name for your baby boy? The baby boy name Rex is 3 letters long, and contains 1 vowel(s) and 2 consonant(s). Rex is a baby boy name that starts with the letter R and ends in the letter X. The baby boy name Rex has a popularity of 32% and is ranked 681 in the list of top 1000 most popular baby boy names. If Rex isn't the ideal name for your baby boy then take a look here for some randomly generated names. Hopefully you'll find a more suitable first name for your baby boy than Rex!