The animal charity was contacted by members of the public who reported that the cub had been struggling for weeks and was spotted in the Acocks Green area of Birmingham.
An animal rescue officer attended and found the fox was lethargic and, after removing the litter, transferred it to a wildlife centre for rehabilitation.
RSPCA animal rescue officer Cara Gibbon said: “It is so sad and heartbreaking to know that this poor fox wouldn’t have been in this situation if someone had disposed of their litter correctly in the first place.
“Thankfully we were able to safely catch him and remove the litter and we transferred him to a wildlife centre where he was checked over. He was emaciated and dehydrated, likely because he hasn’t been able to eat or drink properly for three weeks - but thankfully he’s now getting the treatment he needs.”
The RSPCA has received more than 10,000 calls over the past three years about animals affected by litter.
With an average of almost 10 reports per day taken by the charity about animals found severely injured, trapped, mutilated, choked or even dead from carelessly discarded litter of all kinds, the RSPCA is urging people to do their bit to protect animals by disposing of litter correctly.
RSPCA scientific officer Evie Button said: “Litter is one of the biggest hazards our wildlife faces today. Our staff deal with thousands of incidents every year where animals have been impacted by carelessly discarded litter - and what they are seeing is probably just the tip of the iceberg.
"Sadly, for every animal we’re able to help there are probably many that go unseen, unreported and may even lose their lives.
“Animals who get their heads or necks stuck in litter can suffer severe injuries as they struggle to break free and can even suffocate, while others will slowly grow weaker and weaker as they try to hunt or find food or water.
“Our message to the public is simple - do the right thing and throw your litter away to avoid more animals from suffering.”