In the past general relativity was studied mainly as a subject in mathematical physics. But now it is recognized as an indispensable theoretical framework for cosmology and astrophysics. The discovery of a black hole solution dates back to 1916, soon after the discovery of general relativity. Since then, the properties of black holes have been studied extensively. In recent years, many new sequence of higher-dimensional black hole solutions have been discovered, and their perturbative properties have been clarified. In addition to that, there were remarkable developments in simulating physical/astrophysical systems that include black holes.

In cosmology, Friedmann universe models based on general relativity dates back to 1922. Since then general relativity has been an essential factor in cosmological model building. Meanwhile, the basics of relativistic cosmology have been reinforced by various observations, and new paradigms such as Big Bang and inflation have been established. Cosmology has been also extended to higher spacetime dimensions in recent years. Currently, the dark energy problem is highlighted as a major problem in cosmology, and modified gravity theories have been discussed in depth as one of the attractive possibilities to solve the dark energy problem.

In this academic situation, new research institutes scoping at cosmology and gravitation have been founded in many Asian countries successively. We are then determined to promote collaborative investigations in cosmology and gravitation and to educate the young generation in the Asia-Pacific region. It will bring an immeasurable effect on the future of this field. Under such thoughts, "Asia-Pacific School/Workshop on Cosmology and Gravitation" has been held each year since 2007.

This workshop consists of two parts: lectures by invited speakers and presentations by participants.
Topics covered by the workshop include:
 Gravitational waves
 Numerical relativity
 Black hole physics
 Cosmic microwave backgrounds
 Inflationary universe
 Dark matter and dark energy
 String cosmology
 Quantum gravity

This workshop is held as one of the YITP workshops.
For acknowledgments please include the workshop number;
YITP-W-11-26.
It is also supported by the Asia-Pasific Center for Theoretical Physics (APCTP),
by JSPS Grant-in-Aid for Scientific Research (A) No. 21244033,
and by JSPS Grant-in-Aid for Creative Scientific Research No. 19GS0219.

We are also happy to announce that EPL, A Letters Journal Exploring the Frontiers of
Physics, supports the workshop by providing Awards for Excellent Talks
by Students and Postdocs. Winners will receive a certificate and a prize.
Details will be announced during the workshop.