thumbnail|Line-out, [[Stade Toulousain|Toulouse vs. Lyon OU, in a Top 14 match at Stade Ernest-Wallon]]
A line-out or lineout is a means by which, in rugby union, play is restarted after the ball has gone into touch. When the ball goes out of the field of play, the opposing team is normally awarded a line-out; the exception is after the ball is kicked into touch from a penalty kick, when the team that was awarded the penalty throws into the line-out. <!-- 50-22 redirects here-->In 2021 World Rugby began to trial what was dubbed the "50:22" (or "50–22") rule, wherein the kicking team has the throw-in if the ball travels from the kicker's half and bounces beyond the opposing 22-metre line. This was inspired by rugby league's 40/20 kick.
A line-out is formed by players from each team lining up inside the touchline, at 90° to it. A player from the side that did not put the ball into touch then throws the ball back into play.
A line-out is one of the two methods of restarting play after the ball has gone into touch, the other is the "quick throw-in" (sometimes referred to as a quick line-out). Due to the specific rules placed on quick throw-ins they are uncommon in a rugby match, with the majority of restarts from touch taking the form of a line-out.
Line-outs
Position of line-out
thumbnail|Wales (red) win a lineout against England in the 2004 [[Six Nations Championship. England have chosen not to compete for the ball in the air, but are ready to drive into the ball carrier when he lands.]]
thumbnail|In this line attacking line-out, France (blue) threatens on the 5 metre line, and the Welsh defence mass to stop the drive. Note that the non-throwing hooker (#2, Red) is obliged to stand within 5 metres of the touch line. Six Nations, 2004
Where the line-out is taken depends on the manner in which the ball was played into touch. If it is kicked directly into touch, without first landing in the field-of-play or touching the referee or an opponent who is not in touch, the line-out is formed in line with the spot from where it was kicked, with two exceptions: if the kick was a penalty kick or if the kicker had at least one foot on or behind his own 22-metre line, the line-out is formed at the spot where the ball crossed the touch-line.
A player in the line-out will attempt either to catch the ball or to knock it back to a "receiver", a player from their own side (often the scrum-half but sometimes another forward) who is standing close to the line-out on their side of the pitch and in a position to receive such a ball. Each team may have, at most, one receiver at a line-out.
Players not forming part of the line-out, or acting as receiver, must stay at least behind the line at which the line-out is formed until the line-out is over; the only exception is if the line-out is formed within 11 yards of a team's goal-line, when they need only retreat behind the goal-line.
The line-out was originally contested with both teams jumping unsupported to retrieve the ball. However, lifting in the line-out was legalised in 1999 under Law 18 of the World Rugby laws.
Players must not interfere with the opposition during the line-out. In particular, they must not interfere with or tackle a jumper while his feet are off the ground, or interfere with players supporting him; such actions are deemed to be dangerous play and will be penalised with a penalty kick. If he does so, an opponent may also run forward to contest possession. Players who are taking part in the line-out may move beyond the 15-metre line as soon as the ball leaves the thrower's hands. For a quick throw-in to be legal, the ball can not have been touched by any other person (player or non-player), apart from the player taking the throw or the opponent who may have carried the ball into touch and it can only be taken between the point of the ball leaving the field and the thrower's own goal line, unless a kick-off or restart kick goes straight into touch, in which case the ball may be taken up to the 50 metre line.