This is the first paper of a series that will present data and scientific results from the WINGS project , a wide-field , multiwavelength imaging and spectroscopic survey of galaxies in 77 nearby clusters .
The sample was extracted from the ROSAT catalogs of X-Ray emitting clusters , with constraints on the redshift ( 0.04 < z < 0.07 ) and distance from the galactic plane ( { | } b { | } \geq 20 deg ) .

The global goal of the WINGS project is the systematic study of the local cosmic variance of the cluster population and of the properties of cluster galaxies as a function of cluster properties and local environment .
This data collection will allow the definition of a local , ’ zero-point ’ reference against which to gauge the cosmic evolution when compared to more distant clusters .

The core of the project consists of wide-field optical imaging of the selected clusters in the B and V bands .
We have also completed a multi-fiber , medium-resolution spectroscopic survey for 51 of the clusters in the master sample .
The imaging and spectroscopy data were collected using , respectively , the WFC @ INT and WYFFOS @ WHT in the northern hemisphere , and the WFI @ MPG and 2dF @ AAT in the southern hemisphere .
In addition , a NIR ( J , K ) survey of \sim 50 clusters and an H _ { \alpha } + U survey of some 10 clusters are presently ongoing with the WFCAM @ UKIRT and WFC @ INT , respectively , while a very-wide-field optical survey has also been programmed with OmegaCam @ VST .

In this paper we briefly outline the global objectives and the main characteristics of the WINGS project .
Moreover , the observing strategy and the data reduction of the optical imaging survey ( WINGS-OPT ) are presented .
We have achieved a photometric accuracy of \sim 0.025 mag , reaching completeness to V \sim 23.5 .
Field size and resolution ( FWHM ) span the absolute intervals ( 1.6-2.7 ) Mpc and ( 0.7-1.7 ) kpc , respectively , depending on the redshift and on the seeing .
This allows the planned studies to obtain a valuable description of the local properties of clusters and galaxies in clusters .