Connection element adapted to connect to each other at least two panels, each panel being a plate-like element which is delimited by two opposing base surfaces "S" and two pairs of shaped longitudinal edges 12a, 12b which are opposite each other, and having a substantially rectangular profile, of a modular structure, preferably of insulated or refrigerating cells, said connection element comprising: • a main body with a prevalent longitudinal extent along a development axis (X'), said main body being provided with a first wall and a second wall (5, 8) which extend longitudinally along said axis and which are arranged perpendicularly to each other, further comprising • a first projection which is arranged perpendicularly to the first wall and which is connected thereto at a first corner so as to delimit therewith an L-shaped engagement seat which extends longitudinally along the axis and which is dimensioned so as to receive and accommodate an end portion of a first panel, • a second projection which is arranged perpendicularly to said second wall and which is connected thereto at a second corner so as to delimit with said second face a second L-shaped engagement seat which extends longitudinally along said axis and which is dimensioned so as to receive and accommodate an end portion of a second panel, wherein said first projection and said second projection are intended to receive a portion of the base surfaces of the first panel and the second panel and are incident in an internal corner of said connection element and are provided with fixing elements (9, 10) in order to fix the end portion (102a, 102b) of each panel (101a, 101b) to the first or second engagement seat (3, 4) of the main body of the connection element by means of the base surface, the internal corner being provided with a protrusion for removably connecting a covering element to the connection element for covering the fixing means received in the fixing elements (9, 10). • a main body with a prevalent longitudinal extent along a development axis (X'), said main body being provided with a first wall and a second wall (5, 8) which extend longitudinally along said axis and which are arranged perpendicularly to each other, further comprising • a first projection which is arranged perpendicularly to the first wall and which is connected thereto at a first corner so as to delimit therewith an L-shaped engagement seat which extends longitudinally along the axis and which is dimensioned so as to receive and accommodate an end portion of a first panel, • a second projection which is arranged perpendicularly to said second wall and which is connected thereto at a second corner so as to delimit with said second face a second L-shaped engagement seat which extends longitudinally along said axis and which is dimensioned so as to receive and accommodate an end portion of a second panel, wherein said first projection and said second projection are intended to receive a portion of the base surfaces of the first panel and the second panel and are incident in an internal corner of said connection element and are provided with fixing elements (9, 10) in order to fix the end portion (102a, 102b) of each panel (101a, 101b) to the first or second engagement seat (3, 4) of the main body of the connection element by means of the base surface, the internal corner being provided with a protrusion for removably connecting a covering element to the connection element for covering the fixing means received in the fixing elements (9, 10).