The observation of associated production of an ${\rm Y}$(1S) meson with a Z boson and a measurement of the ratio of its fiducial cross section to the fiducial cross section of the Z boson are presented. Both the ${\rm Y}$(1S) meson and the Z boson are identified via decays into a pair of opposite-sign muons. The analysis is based on proton-proton (pp) collision data at $\sqrt{s}$ = 13 TeV, collected with the CMS detector in 2016$-$2018andcorrespondingtoanintegratedluminosityof138fb$^{-1}$. Using the production of the Z boson decaying into four muons as a normalization channel, the ratio of the fiducial cross sections $\sigma$(pp $\to$ Z $+$ ${\rm Y}$(1S))$ℬ$(Z $\to$ ${\mu }^{+}{\mu }^{-}$)$ℬ$(${\rm Y}$(1S) $\to$ ${\mu }^{+}{\mu }^{-}$ ) to $\sigma$(pp $\to$ Z)$ℬ$(Z $\to$ 4$\mu$) is measured to be ${ℛ}_{Z+{\rm Y}(1S)}$ = (21.1 $\pm$ 55 (stat) $\pm$ 0.6 (syst) $\times$ 10${}^{-3}$), where stat and syst denote the statistical and systematic uncertainties, respectively. The result is used to extract the effective double-parton scattering cross section ${\sigma }_{\mathrm{\text{eff}}}$ = 13.0${}_{-3.4}^{+7.7}$. In addition, for the first time, ${\sigma }_{\mathrm{\text{eff}}}$ is measured in bins of the transverse momentum of the ${\rm Y}$(1S) meson or of the Z boson.