There are 7 13-letter words that start with 'sou'.
| soulfulnesses | soundproofing |
| southeasterly | southeastward |
| southernwoods | southwesterly |
| southwestward | |
Note: These 7 13-letter words that start with 'sou' are found from the USA & Canada version of the tournament Scrabble word list.
Also see words start with sout, sour, soun, soul, soup, sous, soub, souv, soug, souc, souf, souk, soua, soud.
4-letter words start with 'sou' (5)