An isolation effort focused on sporogenous Actinomycetota from the Tagus estuary in Alcochete, Portugal, yielded a novel actinomycetal strain, designated MTZ3.1^T, which was subjected to a polyphasic taxonomic study. MTZ3.1^T is characterised by morphology typical of members of the genus Streptomyces , with light beige coloured substrate mycelium, which does not release pigments to the culture medium and with helicoidal aerial hyphae that differentiate into spores with a light-grey colour. The phylogeny of MTZ3.1^T, based on the full 16S rRNA gene sequence, indicated that its closest relatives were Streptomyces alkaliterrae OF1^T (98.48 %), Streptomyces chumphonensis KK1-2^T (98.41 %), Streptomyces albofaciens JCM 4342^T (98.34 %), Streoptomyces paromomycinus NBRC 15454^T (98.34 %) and Streptomyces chrestomyceticus NRBC 13444^T (98.34 %). Moreover, average nucleotide identity (ANI), average amino acid identity (AAI) and digital DNA–DNA hybridisation (dDDH) are below the species cutoff values (ANI 67.70 and 68.35 %, AAI 77.06 and 76.71 % and dDDH 22.10 and 21.50 % for S. alkaliterrae OF1^T and S. chumphonensis KK1-2^T, respectively). Whole genome sequencing revealed that MTZ3.1^T has a genome of 5 644 485 bp with a DNA G+C content of 71.29 mol% and 5044 coding sequences. Physiologically, MTZ3.1^T is strictly aerobic, able to grow at 15–37 °C, optimally at 25 °C and between pH5 and 8 and showed high salinity tolerance, growing with 0–10 %(w/v) NaCl. Major cellular fatty acids are C_{15 : 0}, iso-C_{15 : 0}, anteiso-C_{15 : 0} and iso-C_{16 : 0}. Furthermore, it was able to utilise a variety of nitrogen and carbon sources. Antimicrobial screening indicated that MTZ3.1^T has potent anti- Staphylococcus aureus activity. On the basis of the polyphasic data, MTZ3.1^T is proposed to represent a novel species, Streptomyces meridianus sp. nov. (= CECT 30416^T = DSM 114037^T=LMG 32463^T).