Yes, generally, you must have consent from your landlord. If you don’t, your landlord may have grounds for eviction based on a breach of your tenancy agreement.
Landlords can’t refuse a Sublet Agreement without reasonable cause. However, a landlord has an interest in who is a subtenant and can refuse to provide consent in some circumstances. An example is if a potential subtenant can’t pass a credit check during an application screening.
Check your country’s tenancy acts for further guidelines your landlord must follow in consenting to sublet.