RP 1, RP-1, RP.1, RP1, or variant may refer to:

• RP-1, Rocket Propellant 1
• RP1, retinitis pigmentosa 1 protein
• RP1 asteroid
  • 5580 Sharidake or 1988 RP1, asteroid Sharidake, RP1 from 1998, the 5580th asteroid catalogued
  • (12728) 1991 RP₁, RP1 from 1991, the 12728th asteroid catalogued
  • 12576 Oresme or 1999 RP1, asteroid Oresme, RP1 from 1999, the 12576th asteroid catalogued
• Mitsubishi RP-1, helicopter
• Rensselaer RP-1, manned glider
• Radioplane RP-1, UAV
• Ready Player One, novel by Ernest Cline

RP-1 (alternately, Rocket Propellant-1 or Refined Petroleum-1) is a highly refined form of kerosene outwardly similar to jet fuel, used as rocket fuel. Although having a lower specific impulse than liquid hydrogen (LH₂), RP-1 is cheaper, stable at room temperature, far less of an explosion hazard and far denser. RP-1 is significantly more powerful than LH₂ by volume. RP-1 also has a fraction of the toxicity and carcinogenic hazards of hydrazine, another room-temperature liquid fuel. Thus, kerosene fuels are more practical for many uses.

In real analysis, the projectively extended real line (also called the one-point compactification of the real line, or simply real projective line), is the extension of the number line by a point denoted . It is thus the set (where is the set of the real numbers), sometimes denoted by The added point is called the point at infinity, because it is considered as a neighbour of both ends of the real line. More precisely, the point at infinity is the limit of every sequence of real numbers whose absolute values are increasing and unbounded.