A process and an ultracompact plant for the endless production of hot rolled steel strip comprising an ingot mold (15) that produces a very thin slab, having narrow sides with thickness in the range between 40 and 55 mm and a central swelling, at a speed in the range between 4 and 16 m/min. Such a slab, which displays a core in which the steel is still liquid, is passed through a vertical pre-rolling device (16) that reduces the thickness of the slab and flattens it. The solidified slab may thus be subjected to a first mild rolling by a conveyor (17) and, by forming a free curve, takes a horizontal position where it is subjected to a first surface descaling, a first rolling, a heating in an inductor (23), a second surface descaling and a series of reductions in a rolling mill (30) formed by at least two stands, by maintaining its temperature along the mill above the recrystallization point Ar3. Downstream of the rolling mill (30) there are provided a roller runway with cooling showers, a flying shear (33) for cutting to length the strip produced, pinch rolls and at least two spinning wheels (34) for the formation of coils of the hot rolled strip.