There are 8 recipients (asnaf) of Zakat as mentioned in Surah al-Taubah (60) :

“Zakat expenditures are only for the poor and for the needy and for those employed to collect [Zakat] and for bringing hearts together [for Islam] and for freeing captives [or slaves] and for those in debt and for the cause of Allah and for the [stranded] traveler - an obligation [imposed] by Allah. And Allah is Knowing and Wise.”

Thus, it is clear that orphans and widows are not amongst the recipients entitled to receive Zakat.

However, if they fall in any of the category of the above mentioned asnaf, then in that situation they are eligible to receive Zakat.