| Cover | Aug. 12, 2021 |
| Cover [Abstract] | |
| Document Type | 8-K |
| Amendment Flag | false |
| Document Period End Date | Aug. 12, 2021 |
| Entity File Number | 001-36304 |
| Entity Registrant Name | PHIO PHARMACEUTICALS CORP. |
| Entity Central Index Key | 0001533040 |
| Entity Tax Identification Number | 45-3215903 |
| Entity Incorporation, State or Country Code | DE |
| Entity Address, Address Line One | 257 Simarano Drive |
| Entity Address, Address Line Two | Suite 101 |
| Entity Address, City or Town | Marlborough |
| Entity Address, State or Province | MA |
| Entity Address, Postal Zip Code | 01752 |
| City Area Code | (508) |
| Local Phone Number | 767-3861 |
| Written Communications | false |
| Soliciting Material | false |
| Pre-commencement Tender Offer | false |
| Pre-commencement Issuer Tender Offer | false |
| Title of 12(b) Security | Common Stock, par value $0.0001 |
| Trading Symbol | PHIO |
| Security Exchange Name | NASDAQ |
| Entity Emerging Growth Company | false |
