A bstract Forward top quark pair production is studied in pp collisions in the μeb final state using a data sample corresponding to an integrated luminosity of 1.93 fb −1 collected with the LHCb experiment at a centre-of-mass energy of 13 TeV. The cross-section is measured in a fiducial region where both leptons have a transverse momentum greater than 20 GeV and a pseudorapidity between 2.0 and 4.5. The quadrature sum of the azimuthal separation and the difference in pseudorapidities, denoted Δ R , between the two leptons must be larger than 0.1. The b -jet axis is required to be separated from both leptons by a Δ R of 0.5, and to have a transverse momentum in excess of 20 GeV and a pseudorapidity between 2.2 and 4.2. The cross-section is measured to be $$ {\sigma}_{t\overline{t}}=126\pm 19\left(\mathrm{stat}\right)\pm 16\left(\mathrm{syst}\right)\pm 5\left(\mathrm{lumi}\right)\mathrm{f}\mathrm{b} $$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:msub> <mml:mi>σ</mml:mi> <mml:mrow> <mml:mi>t</mml:mi> <mml:mover> <mml:mi>t</mml:mi> <mml:mo>¯</mml:mo> </mml:mover> </mml:mrow> </mml:msub> <mml:mo>=</mml:mo> <mml:mn>126</mml:mn> <mml:mo>±</mml:mo> <mml:mn>19</mml:mn> <mml:mfenced> <mml:mi>stat</mml:mi> </mml:mfenced> <mml:mo>±</mml:mo> <mml:mn>16</mml:mn> <mml:mfenced> <mml:mi>syst</mml:mi> </mml:mfenced> <mml:mo>±</mml:mo> <mml:mn>5</mml:mn> <mml:mfenced> <mml:mi>lumi</mml:mi> </mml:mfenced> <mml:mi>f</mml:mi> <mml:mi>b</mml:mi> </mml:math> where the first uncertainty is statistical, the second is systematic, and the third is due to the luminosity determination. The measurement is compatible with the Standard Model prediction.