BACKGROUND Natural products with distinctive pharmaceutical activities are considered as the main source of new herbal drugs, functional foods and cosmetic additives. Rumex algeriensis is an endemic medicinal plant with no accessible information about its chemical profile and biological activities. OBJECTIVE In the quest for new sources of biologically-active compounds, we intended in the present work to undertake a comprehensive characterisation of phytochemical compounds from Rumex algeriensis flowers and stems hydro-methanolic extract. METHODS Chemical profiles were evaluated by a rapid analytical method reversed-phase high-performance liquid chromatography (RP-HPLC) coupled to electrospray ionisation-quadrupole-time-of-flight mass spectrometry (ESI-QTOF-MS) and tandem mass spectrometry (MS/MS) using negative and positive ions modes. RESULTS In this work, 44 bioactive compounds were tentatively identified using high mass accuracy data and confirmed by MS/MS experiments, among which five compounds were reported for the first time in the Polygonaceae family. These compounds were classified as sugars, hydroxybenzoic acids, hydroxycinnamic acids, flavonols, flavanones, flavone, flavanols, condensed tannins, hydrolysable tannins and their conjugated derivatives. CONCLUSIONS The obtained results highlighted that Rumex algeriensis, even though undervalued and unexplored, contributes to the preclinical knowledge that could be considered as a renewable source of nutraceutical compounds that may be exploited in novel herbal medicinal products, in the food, pharmaceutical and nutraceutical industries.