No, squirrels are not marsupials. Squirrels belong to the order Rodentia, which includes animals like mice, rats, and beavers. Marsupials, on the other hand, belong to the infraclass Marsupialia and include animals like kangaroos, koalas, and opossums.
The main difference between rodents and marsupials lies in their reproductive systems. Marsupials give birth to relatively undeveloped young, which then continue to develop outside the womb, often in a pouch. Rodents, including squirrels, give birth to more developed young that do not require a pouch for further development.
So, while both squirrels and marsupials are mammals, they are quite different in terms of their classification and reproductive strategies.