Inverse heat conduction analysis provides an efficient approach for estimating the thermophysical properties of materials, the boundary conditions, or the initial conditions. In this paper, two-dimensional transient nonlinear inverse heat conduction problems are investigated, for estimating time-and space-dependent boundary heat flux, as well as the temperature-dependent thermal conductivities. Modifications are carried out to extend the previous onedimensional inversion algorithm to solve the two-dimensional transient nonlinear heat conduction problem, to overcome the frequently occurring divergence issues, and to improve the stability of the inversion algorithm. Boundary-only measurements are used as additional information, and a dimensionless objective function is adopted. In the direct problem, formulations for solutions to the two-dimensional transient nonlinear heat conduction problem are derived and validated. Numerical examples show that the inversion algorithm is effective, efficient, accurate, and robust, for recovering multiple parameters, with and without a functional form. Nomenclature a = coefficient to be recovered in Eq. (27), W∕m 2 b = coefficient to be recovered in Eq. (27), 1∕s c = heat capacity, J∕kg · K d = coefficient to be recovered in Eq. (27) E rms = root mean square deviation betweenthe recovered/ inverted and the exact/real values Fo = Fourier number Fo x = λ∕ρc × Δτ∕Δx 2 Fo y = λ∕ρc × Δτ∕Δy 2 fX = real function with variable X fX ih = complex function with real variable X and imaginary part h, to be expanded into Taylor series h = imaginary part in complex variable i = the ith node numberalong x coordinate j = the jth node numberalong y coordinate K = the iteration number k = the kth time interval L = the length of the modeled object in x direction, m M = total number of measured temperatures N = total number of inverted parameters N x = total number of nodes along x coordinate N y = total number of nodes along y coordinate q = heat flux, W∕m 2 R = residual vector S = dimensionless objective function t = temperature, K W = the width of the modeled object in y direction, m w = relaxation factor X = real variable in function f x = x coordinate, m y = y coordinate, m z = vector of inverted parameters Greek γ = exact value Δ = change in variable ζ = random measurement error η = random number λ = thermal conductivity, W∕m · K ξ = small positive number ρ = density, kg∕m 3 χ = recovered/inverted value τ = heating time, s Subscripts 0 = initial time b = bottom exact = exact i = the ith component of a vector i 1∕2 = midpoint between nodes i and i 1 i; j = node location at the ith node number along the x direction, and the jth node along the y direction j = the jth component of a vector l = left r = right u = upper Superscripts 0 = initial guess * = measured