We present a data-driven model to reconstruct nonlinear dynamics from a very sparse times series data, which relies on the strength of the echo state network (ESN) in learning nonlinear representation of data. With an assumption of the universal function approximation capability of ESN, it is shown that the reconstruction problem can be formulated as a fixed-point problem, in which the trajectory of the dynamical system is a fixed point of the ESN. An under-relaxed fixed-point iteration is proposed to reconstruct the nonlinear dynamics from a sparse observation. The proposed fixed-point ESN is tested against both univariate and multivariate chaotic dynamical systems by randomly removing up to 95% of the data. It is shown that the fixed-point ESN is able to reconstruct the complex dynamics from only 5 ∼ 10% of the data. For a relatively simple non-chaotic dynamical system, the numerical experiments on a forced van der Pol oscillator show that it is possible to reconstruct the nonlinear dynamics from only 1∼2% of the data. particular, in [8,9], it is shown that ANN is capable of predicting the dynamics of a chaotic attractor. When training an ANN for the modeling of a dynamical system, it is typical to use a sufficiently long time series data, so that the ANN fully explores the phase space. Given the huge amount of training data, it is unclear whether the long-term forecast capability of ANN is due to a high dimensional interpolation in a phase space, similar to the delay-coordinate embedding [10,11], or because ANN really learns the nonlinear dynamics. As a first step to answer this question, we first consider the problem, where only a partial observation of a time series data is available. We investigate if ANN can reconstruct the nonlinear dynamics from the incomplete information.Reconstructing dynamics from an incomplete observation has practical applications in many physical, biological, and engineering problems, where the state of the system is accessible only through a sensor network. For example, in geophysics, it is not uncommon to find time series data, which contains a large amount of missing information or is irregularly sampled, due to sensor malfunction, atmospheric conditions, or physical limitations of the sensors [12,13,14]. When a priori knowledge on the physical system is available, one of the standard approaches to reconstruct the nonlinear dynamics from an incomplete data set is to design a statistical model that incorporates the physical knowledge [15,16,17]. In [18], it is shown that a high-resolution temporal dynamics can be reconstructed from a low-resolution time series data, which has a 10 times lower time resolution, by using only a subset of the governing equations. Incorporating the physics knowledge on the training of ANN, [6] proposed "physics informed neural network", which can recover the complex nonlinear dynamics from only a small fraction of the data.It is challenging to reconstruct nonlinear dynamics without having any prior knowledge on the underlying process. There are three ...