PROSPECTUS SUMMARY

This summary highlights selected information appearing elsewhere in this prospectus. Because it is abbreviated, this summary does not contain all of the information that you should consider before investing in our common units. While this summary highlights what we consider to be the most important information about us, you should read the entire prospectus carefully, including the historical combined carve-out and unaudited pro forma combined carve-out financial statements and the notes to those financial statements. The information presented in this prospectus assumes (i) an initial public offering price of $         per common unit (the mid-point of the price range set forth on the cover page of this prospectus) and (ii) unless otherwise indicated, that the underwriters’ option to purchase additional common units is not exercised. You should read “Risk Factors” beginning on page 21 for more information about important risks that you should consider carefully before investing in our common units.

Unless the context otherwise requires, references in this prospectus to “our partnership,” “our,” “us,” “we” or like terms refer to “Westlake Chemical Partners LP” and, unless otherwise specified, Westlake Chemical OpCo LP and Westlake Chemical OpCo GP LLC. When used in a historical context, “our,” “us,” “we” or like terms refer to the ethylene business, including feedstock costs and revenue associated with the sale of ethylene and co-products, conducted by Westlake Chemical Corporation and its subsidiaries, a portion of which will be contributed to Westlake Chemical OpCo LP in connection with the closing of this offering. References in this prospectus to “our general partner” refer to Westlake Chemical Partners GP LLC. References to “OpCo” refer to Westlake Chemical OpCo LP, which is a newly created limited partnership owned by us and Westlake Chemical Corporation and its subsidiaries. References to “Westlake” refer collectively to Westlake Chemical Corporation and its subsidiaries, other than us, our general partner, OpCo and Westlake Chemical OpCo GP LLC, OpCo’s general partner. We will own a 10% limited partner interest and the general partner interest in OpCo. We will consolidate OpCo in our financial statements. We have provided definitions for some of the terms we use to describe our business and industry and other terms used in this prospectus in the “Glossary of Terms” attached as Appendix B to this prospectus.

Westlake Chemical Partners LP

Overview

We are a Delaware limited partnership recently formed by Westlake to operate, acquire and develop ethylene production facilities and related assets. Westlake is a vertically integrated, international manufacturer and marketer of basic chemicals, polymers, and fabricated building products. Our business and operations are conducted through OpCo, a recently formed partnership between Westlake and us. At the consummation of this offering, our assets will consist of a 10% limited partner interest in OpCo as well as the general partner interest in OpCo. Because we own OpCo’s general partner, we have control over all of OpCo’s assets and operations. Westlake has retained a 90% limited partner interest in OpCo and will retain a significant interest in us through its ownership of our general partner as well as         % of our limited partner units (consisting of              common units and all of the subordinated units) and our incentive distribution rights.

OpCo’s assets will be comprised of three ethylene production facilities, which convert primarily ethane into ethylene, with an aggregate annual capacity of approximately 3.4 billion pounds and a 200-mile ethylene pipeline. OpCo will derive substantially all of its revenue from its ethylene production facilities. Ethylene is the world’s most widely used petrochemical in terms of volume and is a key building block used to produce a number of key derivatives, such as polyethylene (“PE”) and polyvinyl chloride (“PVC”), which are used in a wide variety of end markets including packaging, construction and transportation. Westlake’s downstream PE and PVC production facilities will consume a substantial majority of the ethylene produced by OpCo. OpCo

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will generate revenue primarily by selling ethylene to Westlake and others, as well as through the sale of co-products of ethylene production, including propylene, crude butadiene, pyrolysis gasoline and hydrogen. Our sole revenue generating asset will be our 10% limited partner interest in OpCo.

In connection with this offering, OpCo will enter into a 12-year ethylene sales agreement with Westlake, under which Westlake will agree to purchase 95% of OpCo’s planned ethylene production each year on a cost-plus basis that is expected to generate a fixed margin per pound of $0.10 (the “Ethylene Sales Agreement”). We believe this agreement will promote more stable and predictable cash flows for OpCo. Any ethylene not sold to Westlake and all co-products that are produced by OpCo will be sold to third parties on either a spot or contract basis. OpCo will also enter into a feedstock supply agreement with Westlake that will supply OpCo with all of the ethane (and any other feedstocks) required for OpCo to produce ethylene under the Ethylene Sales Agreement (the “Feedstock Supply Agreement”).

OpCo primarily uses ethane (a component of natural gas liquids, or NGLs) to produce ethylene. Approximately 66.5% of global ethylene production is based on higher priced feedstocks (primarily naphtha, as well as butane and propane) whose prices are linked to global oil prices. As a result, global ethylene and ethylene derivative prices have generally been linked to movements in global oil prices (principally Brent crude prices) for more than 20 years. In the U.S., technological advances in horizontal drilling and fracturing techniques in shale formations have dramatically increased the production of oil and gas and resulted in the oversupply of ethane. The spread between U.S. ethane and global oil prices has provided a margin advantage for U.S. ethane-based ethylene producers, such as OpCo. Throughout 2012 and 2013, production costs for U.S. ethane-based ethylene producers were significantly lower than global ethylene production facilities utilizing naphtha and other feedstocks. This feedstock cost advantage for U.S. ethane-based ethylene producers as compared to Asia naphtha-based ethylene producers has resulted in a positive cash cost differential that has ranged from $0.23 per pound to $0.48 per pound, and averaged $0.38 per pound, since 2012. Over the last decade, cash margins of U.S. ethane-based ethylene producers were above $0.10 per pound every year other than 2009, when cash margins were below $0.10 per pound due to the global economic recession.

Given Westlake’s significant ownership interest in us following this offering, we believe Westlake is incentivized to offer us the opportunity to purchase additional assets that it owns, including additional interests in OpCo, although it is under no obligation to do so. We may also pursue organic growth opportunities at OpCo as well as acquisitions from third parties, which could be effected jointly with Westlake. OpCo currently plans to expand the capacity of one of its ethylene production facilities by approximately 250 million pounds in late 2015 or early 2016.

For the year ended December 31, 2013, OpCo had pro forma revenues of approximately $1,198.8 million, pro forma EBITDA of approximately $369.6 million and pro forma net income of approximately $295.5 million. For the same time period, we had pro forma EBITDA (net of noncontrolling interest) of approximately $37.0 million and pro forma net income (net of noncontrolling interest) of approximately $29.6 million. For the three months ended March 31, 2014, OpCo had pro forma revenues of approximately $333.4 million, pro forma EBITDA of approximately $90.9 million and pro forma net income of approximately $71.4 million. For the same time period, we had pro forma EBITDA (net of noncontrolling interest) of approximately $9.1 million and pro forma net income (net of noncontrolling interest) of approximately $7.1 million. Please read “—Summary Historical and Pro Forma Combined Carve-out Financial and Operating Data—Non-GAAP Financial Measure” for the definition of EBITDA and a reconciliation of EBITDA to net income, on a historical basis and pro forma basis, and to cash flow from operating activities, on a historical basis, which reconciliation is presented in accordance with generally accepted accounting principles (“GAAP”).

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Our Assets and Operations

Our sole revenue generating asset will be our 10% limited partner interest in OpCo. We will also own the general partner interest of OpCo. OpCo, in turn, will own:

As the owner of the general partner interest of OpCo, we will control all aspects of the management of OpCo, including its cash distribution policy. See “Business—OpCo’s Assets.”

Ethylene Production Facilities . OpCo operates three ethylene production facilities that are situated on real property leased to OpCo by Westlake pursuant to two 50-year site lease agreements. Ethylene can be produced from either NGL feedstocks, such as ethane, propane and butane, or from petroleum-derived feedstocks, such as naphtha. Lake Charles Olefins and Calvert City Olefins use ethane primarily as their feedstock. Calvert City Olefins can also use propane as a feedstock and Petro 2 can also use an ethane/propane mix, propane, butane or naphtha as a feedstock.

The following table provides information regarding OpCo’s ethylene production facilities as of June 30, 2014:

Longview Pipeline . OpCo owns the Longview Pipeline, which is a 200-mile common carrier ethylene pipeline, with a capacity of 3.5 million pounds per day that runs from Mont Belvieu, Texas to the Longview, Texas chemical complex, which includes Westlake’s Longview PE production facility.

Our Ethylene Sales Agreement with Westlake

In connection with this offering, OpCo will enter into the Ethylene Sales Agreement with Westlake. The Ethylene Sales Agreement will have an initial term through December 31, 2026 and will automatically renew thereafter for successive 12-month terms unless terminated by either party. The Ethylene Sales Agreement requires Westlake to purchase 95% of OpCo’s planned ethylene production each year, subject to certain exceptions and a maximum commitment of 3.8 billion pounds per year. If OpCo’s actual production is in excess of planned ethylene production, Westlake will have the option to purchase up to 95% of production in excess of planned production.

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Westlake’s purchase price for the minimum commitment of ethylene under the Ethylene Sales Agreement will be calculated on a per pound basis and includes:

Westlake’s purchase price for any ethylene produced in excess of the planned production amount will generally equal OpCo’s estimated variable costs of producing the incremental ethylene, plus a $0.10 per pound margin. The estimated operating costs and maintenance capital expenditures and other turnaround expenditures will be adjusted at the end of each year to reflect certain changes in forecasted costs. If OpCo’s actual operating costs and maintenance capital expenditures and other turnaround expenditures are higher than the estimate for any year, or OpCo’s actual production is below the planned production amount upon which the per pound operating costs and maintenance capital expenditures and other turnaround expenditures are based, OpCo will be entitled to include in the fee for the succeeding year a surcharge to recover the resulting shortfall. If these costs are lower than estimated, OpCo will retain the difference, but such difference may be reflected in periodic downward adjustments to the total estimated costs. The result of the fee structure is that OpCo should recover the portion of its total operating costs and maintenance capital expenditures and other turnaround expenditures attributable to Westlake’s ethylene purchases. Approximately 5% of OpCo’s ethylene production will be sold at market rates on either a spot or contract basis to third parties. Average U.S. industry margins for producing ethane-based ethylene are currently substantially in excess of $0.10 per pound, and averaged approximately $0.46 per pound since 2013.