At 6.55pm on Thursday 7 January police were called to a residential address in Cedars Gardens, Withdean, Brighton, where the woman was found deceased. The 17-year-old boy has been arrested on suspicion of murder and is currently in custody for interview and further enquiries.
The boy and woman are known to each other.
Police are not currently looking for anyone else in relation to the crime and there is no risk to the local community.
The investigation, which is being carried out by detectives from the Surrey and Sussex Major Crime Team working with local officers, is at an early stage and no further information is available at present.