A saddle riding vehicle, comprising: a unit swing engine that includes a crankcase and a cylinder portion having a cylinder axis extending from the crankcase in a vehicle fore-aft direction and that is swingably supported on a vehicle body frame; an exhaust pipe connected with the cylinder portion; a catalyst unit disposed in the exhaust pipe; an exhaust gas sensor (140, 240, 340, 440) disposed in the exhaust pipe, and a muffler that is a downstream end portion of the exhaust pipe, wherein the unit swing engine is supported on the vehicle body frame via a vehicle body-side rocking shaft disposed superior to the unit swing engine, in a side view, at least a part of the catalyst unit is disposed inferior to the cylinder portion and is disposed in a region between a first imaginary line and a second imaginary line, the first imaginary line connecting the vehicle body-side rocking shaft and a front end of the crankcase, the second imaginary line connecting an exhaust pipe connection portion of the cylinder portion, with which an end of the exhaust pipe is connected, and the vehicle body-side rocking shaft, the exhaust pipe includes an upstream side exhaust pipe located upstream of the catalyst unit, characterized in that the upstream side exhaust pipe includes a downward extension portion that extends from the exhaust pipe connection portion downwardly, a lateral extension portion that extends from a lower end of the downward extension portion toward a side opposite from the muffler in the vehicle width direction, and a curved portion that is bent from an outer end of the lateral extension portion toward a side of the muffler and connected to the catalyst unit disposed posterior to the downward extension portion, and the exhaust gas sensor (140, 240, 340, 440) is disposed in the upstream side exhaust pipe at a position inferior to the cylinder portion. a unit swing engine that includes a crankcase and a cylinder portion having a cylinder axis extending from the crankcase in a vehicle fore-aft direction and that is swingably supported on a vehicle body frame; an exhaust pipe connected with the cylinder portion; a catalyst unit disposed in the exhaust pipe; an exhaust gas sensor (140, 240, 340, 440) disposed in the exhaust pipe, and a muffler that is a downstream end portion of the exhaust pipe, wherein the unit swing engine is supported on the vehicle body frame via a vehicle body-side rocking shaft disposed superior to the unit swing engine, in a side view, at least a part of the catalyst unit is disposed inferior to the cylinder portion and is disposed in a region between a first imaginary line and a second imaginary line, the first imaginary line connecting the vehicle body-side rocking shaft and a front end of the crankcase, the second imaginary line connecting an exhaust pipe connection portion of the cylinder portion, with which an end of the exhaust pipe is connected, and the vehicle body-side rocking shaft, the exhaust pipe includes an upstream side exhaust pipe located upstream of the catalyst unit, characterized in that the upstream side exhaust pipe includes a downward extension portion that extends from the exhaust pipe connection portion downwardly, a lateral extension portion that extends from a lower end of the downward extension portion toward a side opposite from the muffler in the vehicle width direction, and a curved portion that is bent from an outer end of the lateral extension portion toward a side of the muffler and connected to the catalyst unit disposed posterior to the downward extension portion, and the exhaust gas sensor (140, 240, 340, 440) is disposed in the upstream side exhaust pipe at a position inferior to the cylinder portion.